You can add referrals by going to Referrals from left navigation menu and clicking on the Add New button.
The only required field is the person giving a referral - rest of the fields are optional. Following are fields on the Referral's Add New page:
You can edit an existing referral by clicking on the Edit button on the Referral you want to edit from the Referrals screen.
You can delete an existing referral by clicking on the Delete button on the Referral you want to delete from the Referrals screen.