The WP Affiliate plugin has a feature that allows you to manually approve your members.
Step 1) Enable the Settings Option
Go to the settings menu of the affiliate plugin and enable the Manually Approve Affiliate Registration option.
Now, all the affiliate that signup will have an account status of “pending” so they cannot log into the affiliate portal.
Step 2) View the Affiliate Signups
Go to the Manage Affiliates menu to see the newly joined affiliates. You can sort the affiliates listing by the Account Status column to see the pending ones easily.
Step 3) Review and Update Account Status
To approve an affiliate account, edit the affiliate record in question. Change the Account Status from pending to approved.
Step 4) Save the Record
Save the affiliate record. Now this affiliate can log into his affiliate account.
Optionally, you can check the Send Signup Email checkbox before saving. This will send the post registration email to that affiliate. You can customize the email content from the Email Settings menu of the plugin.