Similar to the process for inviting sellers to sell on your marketplace, buyers will have to receive a buyer invitation to buy on your marketplace.
As an admin, you can invite buyers to your marketplace in the admin portal under Buyers, in the User Mgmt. tab.
Click Invite Buyers and type in the buyer’s email address. A buyer invitation will then be sent to them via email.
Alternatively, buyers may indicate their interest in selling on your marketplace by indicating their interest when they are re-directed to the private marketplace page.
You will then see their email on the Waiting list under the Buyers tab in your admin portal. Should you choose to grant access to the buyer, you are able to send them a buyer invitation via email as well.
Once done, the buyer will have to onboard as a buyer via the buyer invitation sent to them through email.
Here is a video link that will assist you in setting up a private marketplace.