Some apps only hand out rewards through an invite. Find one here, use it at sign-up and get the same perk the member who posted it got.
0 brands with an active referral programme.
Most apps ask for the invite code on the last step of registration, in a field called 'invite', 'referral' or 'promo'. A few only apply it if you open the invite link before creating your account.
If the field is missing, close the app, open the referral link from the card and start again.