Shipping is handled by plugins.
Go to Extensions->Plugin Manager and select MyMuse in the type filter. Choose ONE of the following.
MyMuse Shipping Standard
Set up to three choices for your customers. Set the Carrier name (ex. UPS) and method (ex. ground) and set amounts for first item and each additional item.
MyMuse Shipping Price
Set up to two choices for your customers. In each choice set the Carrier name and method and several levels of charges.
Based on percent of total cost of goods.
Related Help Screen.