To refer friends, you'll have to log into your Haven account.
From the Haven iOS app, tap on the 'Earn up to 4% APY' card on your Home Screen, or click on the gift icon on the upper right hand corner of your app. Invite friends by syncing your address book to Haven to text or email them directly, or send them your personalized Haven link. Haven can only provide referral credit when a friend signs up using your link.
On the web, you can refer friends after signing into your account and looking at your spending screen, or by going to your settings tab.