Click on the "Support Us" button.
You'll be redirected to Paypal where you will fill the credendtials input.
After confirming the transaction you'll get an email with download instructions for the mod you've supported us for.
The email also contains a link that will point you to the forum user creation screen. You'll gain access to the forums dedicated to the mods you've supported us for.
If you already have a forum profile, you'll get reminded at the email, besides gaining access to the specific forum of the mod you've supported us for.
Pick a username and password, click submit.
You'll get confirmation of forum profile creation.
Now you'll be able to login to our forums and see your mod's forums.