There are three ways to create parent/child relationships between affiliates:
Enable MLM in your account by creating a level. When you do this, an MLM tab will appear on the affiliate portal in which affiliates can grab a unique recruitment link.
When new affiliates sign up using the affiliate's recruitment link, they will automatically become a child of the affiliate who shared the MLM invite link. You can see an individual affiliate's recruitment link in their affiliate details panel.
You can manually set an affiliate’s parent through the Tapfiliate interface.
To do this, go to Affiliates Overview > Click the affiliate whose parent you would like to set. You can then set the parent affiliate on the right-side panel. You may also do this after accessing their full profile.
Here's a quick video of the process!
It is also possible to set the parent affiliate through the API.