Steps to Forward a Domain to your main domain using GoDaddy's Website
(your domain would have to be with GoDaddy in order for these steps to work.)

1. Login to your account

2. Click 'Domain Manager' on the left

3. In your Domain Manager, check all the boxes that you want pointed to the main Domain Name.

4. Click Forward

5. Click Forward Domain

6. Input the main domain in the 'Forward my domains to:' field.

7. Click OK