Step 1. Login into your Squarespace shopping cart.
Step 2. Under Website option, click on your site.
Step 3. Click on "Edit" beside the Navigation Tab.
Step 4. On the next page, click the "+" sign across the Main Navigation and click on "Link" as shown below.
Step 5. On the Configure Link pop-up, add a Link Title as "Affiliate Sign-up" and add the link for the affiliate sign-up page. Click "Save".