Once a buyer sends an offer that you'd like to accept, the next step is getting paid. You should start a transaction on Escrow.com from the Exchange app. This is done as soon as you accept an offer from your seller. Learn more about why you should only use Escrow to get paid.
Here is a complete guide for transferring and getting paid.
The next step is to prepare your store to be handed over to your buyer. You'll want to make sure that anything you've agreed to sell is changed over to the buyer. This might include domain names, social media accounts, ad accounts, or physical inventory.