Add B2B User
You can create a customer B2B account by going to Income → Customers → B2B Users.
You can create a vendor B2B account by going to Expenses → Vendors → B2B Users.
You will have different Access Level options to choose from when setting up new B2B accounts.
If you would like to see what the B2B site looks like when logged in as a certain user, select their account by clicking on the value in the Login column of the B2B Users list. From there click the Log In As This User button.
You can add multiple customer B2B users at once from Income → Customers → B2B Users using the Add Multiple Customer B2B Users link.