How do I markup an item for sale in my store?
You'll have the option to include a markup percentage when you add a new item to your store or when you edit an existing item.
Please note that you'll need to be verified and have a PayPal account to receive markup earnings. If you're not yet verified, you'll be prompted to do so when you first add a markup to an item.
Related article: How do I list an item in my store?