You can find your friends on your Payments tab.
What if I can’t find my friend?
If you can’t add someone to your Contacts list, check that:
You've allowed SeamPay access to your address book
The phone number on their SeamPay account is right, and they’ve verified it
The phone number on their SeamPay account matches what you have in your phone's contacts
You quit and restart the SeamPay app