The Affiliations process helps to build organization-level links between customers and MSPs. You can find the list of customers and resellers invited or added to the account under Admin Settings | User Access Management > User Groups > Affiliations tab. The Super Admin of the respective account can review the pending Affiliations and approve or reject the request.
Adding customers or resellers is a 2-way process. Suppose an MSP initiates the process to share the products with a customer, the Super Admin of the customer account should review and approve the request to get added to the MSP account. Similarly, if a customer initiates the process to share the products with an MSP account, the Super Admin of the MSP account should review and approve the request.