That's great! You'll get 10% of their earnings if they sign up via your link. Here is how to make a link. First, create a tracking token for each method of referral. I made one for my email referrals, one for my business site that has a link to HubPages, and I also make individual tracker tokens for individual friends if I want to be sure they clicked and signed up. I think one is limited to 20 tokens. Go to "My Account" and click "URL Trackers" - there you can create you tokens and also see the report of exiting tokens.
Next, go to your profile page and at the bottom, click on "link to this page" - select the token you want for that link and it will make it for you. Then copy and paste that link when you send it to your friends via email. You can also send links to people that direct them to your hubs, with the tracking token included. The "link to this page" is at the bottom of all hubs.