Your referral code is listed on the Referrals page of your account. This can be found by clicking on your account name in the upper right hand corner of the page and selecting Referrals from the drop down menu.
On the Referrals page the first thing listed is your Referral code, a 10 character alphanumeric string that is unique to your account. Right next to it is a link that will automatically copy a full link to the Registration page, including your referral code, to your clipboard.
If you are planning to distribute your referral code through electronic means, it may be easier to use the Copy Invite Link option, both for you and for the person you hope to refer to us. However, if you wish to distribute your referral code in some other fashion, say on a card or flyer or some other means it may be easier to simply include the 10 character code and encourage people to use it when they visit the registration page.