What to Do First

1) Go to Components->MyMuse

A welcome Screen with links to various parts of MyMuse and two functions:

a) Add Sample Data

This will fetch a few files from the joomlamymuse site and create some standard categories and one product with two tracks.

Not necessary to use MyMuse. It will give you an idea of how things are set up.

b) Add Euto Zone Tax Rates.

If you are selling in the Euro Zone, this will add tax rates for VAT for all the Eurozone countries.

2) Go to Components->MyMuse->Store
and edit the settings there.

STORE

If you enter a description it can be pointed to with a menu of type MyMuse->MyMuse Store Layout
That view can also show any products labeled as featured, in a blog type layout.

CONTACT

You will want to edit the Contact Info.
You will want to upload your own logo and point to it in the Small Logo field.

EDIT CSS

This is the MyMuse CSS file loaded whenever MyMuse is. Change things as you see fit. You can include whatever you like in your main CSS and not load this, (Store Options->Disable CSS)

DOWNLOAD OPTIONS

Formats: if you just sell MP3s, leave that as the only format. You can also choose to sell multiple versions, example: MP3 and WAV.
The customer will be able to choose the format. If you want different prices for each format, go to Pricing Options->Pricing Model and choose Price by Product.
Now you can set prices in each product for each format.

Download Directory/Download Directory Type: The default is to put files in subdirectories of Downloads Directory, using the artist name and album.

/path/to/your/site/images/A_MyMuseDownloads/artist_alias/product_alias/download.mp3

OR save your files By Format. The path then would be, for example

/path/to/your/site/images/A_MyMuseDownloads/mp3/download.mp3
/path/to/your/site/images/A_MyMuseDownloads/wav/download.wav

Make sure the Downloads Directory points to the full path to your directory. MyMuse will try to determine this on install. The default will be /path/to/your/site/images/A_MyMuseDownloads. There are many ways to find your full path if you don't know it.  http://docs.joomla.org/How_to_find_your_absolute_path

If you set this to something else, make sure the directory exists and that the web server has permission to write to it.

Depending on your server set up, you may be able to put this outside your web directory for maximum security. You will have to use FTP to put files there as it will out of reach of the the Joomla Media Manager. 

Preview Directory/Previews all in one Directory: this is the relative path to the folder holding your previews. The default is to put files in subdirectories of Previews Directory, using the artist name and album.

/path/to/your/site/images/A_MyMusePrviews/artist_alias/product_alias/download.mp3

You can set this to another path but it must be within the web directory.
You can set 'Previews all in one Directory'.

Upload Files: If you set 'Previews all in one Directory' and Download Directory Type: By Format, you can upload all your files to those directories and they will be available when creating albums and tracks.
If you do not, then you should create the artist categories and products first; MyMuse will create the sub-directories, then you can upload your files.

PHYSICAL OPTIONS

If you sell physical products, like CD'd, you probably want to turn on 'Use Shipping'. There are Shipping Plugins to handle the calculations.
'Add Shipping Automatically': if Yes and there is only one shipping option, it will be added so the customer does not have to click through another screen.
'Use Stock': Add Stock numbers to your products and deduct at sale time.
'Check Stock': If stock is at zero, stop the sale with a message.
'Add Zero Stock': Let the customer 'Backorder'. Orders with backordered items are marked in the Orders section.

STORE OPTIONS

Decide what kind of registration you want: Joomla, Full, No Registration. If you are selling physical items, you will want their address. Both Full and No Registration can gather that information. There are User Plugins to handle each one.

PRICING OPTIONS

'Price by Track' lets you set a price for each track. Maybe some are longer or more valuable.
'Price by Product' lets you set the price, in each product, for the various formats you have.

SALES REPORTS

'Owner Group': set which group will have access to its reports. Each artist needs a user account and must be assigned to this group.
'Cut to the Artist': What percentage should go to the artist. Is shown in reports.

2) Create some Categories

3) Create a Product, add some tracks

4) Create a Menu that points to the 'Store and Featured Products' or 'A Single Product'

5) Go to Modules and set up 'Mymuse Module Amplitude'.

By default it is fixed at the bottom. You can edit the module assets/css/amplitude.css, or override it with your own css.

#mymuse-player-container {
position: fixed;
bottom: 0;
left: 50%;
transform: translateX(-50%);
width: 100%;
}

6) Go to plugins 'Mymuse Audio Amplitude'.

Open it and set one or more categories to make playlists for.
It updates each time you save a product so GO TO A PRODUCT, OPEN AND SAVE. 

TESTING

'Shop Test': Any purchase goes through, emails are not sent.
'Debug MyMuse': various things, including Payment Plugin messages, are sent to the Debug Log at components/com_mymuse/log.txt