Navigate to the Object Manager from Setup by selecting the Gear in the top right corner and then clicking Object Manager.
In the Quick Find, search for Contact
Select the intended Contact Record, click Page Layout in the left-side menu then choose the Contact Layout to modify.
In the top menu, select Mobile & Lighting Actions, then in the Quick Find search Referral.
Click and drag the Record a Referral button into the Salesforce Mobile and Lightning Experience Actions portion of the page layout.
The number of buttons already enabled in that section could determine the order in which the buttons are organized. All buttons will appear on the Contact Record but it's worth considering the priority order.
Once the button has been added. Press Save.
Upon refreshing a Contact Record, the button will either appear on the primary record or the user will click the down arrow to utilize the Referral button.
The Record a Referral button can also be added to the Account Record by following the same steps on the Account Record. Be sure to check out Orca's Referral Tracking guide.