Adding Custom Products for Sale

Ther steps would be:
1. Go to Items, the first thing in your Admin
and create a new item with basic info: Use Cheap Thrills Records as the artist for your Merch 
and you can make up a UPC number and use letters, and assign a price.
When titling a T-Shirt try to keep the names the same and put descriptors like [color] or [sizes] in brackets.
2. That takes you to a details page whe you can add info, upload images and importantly provide a quantity of inventory.
That is necessary to activate the BUY button.
3. Now that it is active, folks need a place to shop for your items so you would want to create a category or feature the items in an existing category.
I created a Merch genre for you. 
You can add the Broadtime ID or click the link on the ITEM page that says:

Item Features, Genres, Promos, News, and Charts

and you can link to the genr there.
4. Finally, if desired you may also feature in the home page features under "Store Featured Items.
Let me know and we connect further to walk through it or I can check your work.