You are receiving this error since you don’t have a Facebook page in the Facebook account you are logged in with. You first of all need to open a business Facebook page to which you can add social store to. Since social store can only be added to page, not to a personal profile.
You can easily create a Facebook page here: www.facebook.com/pages/create
After you’ve created a Facebook page, login to your control panel and now click on the “Add Social Store to Facebook Page” button.
You will now get this scroll down menu where you can choose your new page and add to it social store.
If you need any other help setting up social store feel free to add a comment to this thread.