Your referral link is shown on your dashboard. It points to the home page and ends in ?ref= followed by your code.
You can add ?ref=your-code to any page of the main site, for example a help article or the pricing section, and it still counts.
Personalise your code
Select Customize link on your dashboard to choose a code such as your brand or blog name. You can change it once. Links with your old code stop working, so update them everywhere you shared them.