1. Click where it says, "My Profile" at the top left of your page.

2. Scroll down the categories in the left column to the section where it says, "Settings & Options".

3. In that section, 4th option down, click on "Edit Options".

The options are:
Edit Avatar
Edit Signature
Edit Email & Password
Edit Options
Edit Ignore List

4. Scroll to the bottom of that page where it says, "Miscellaneous Options".

5. There is a section called, "Forums To Exclude From View". You can select forums you want to hide there.

6. Click on "Save Changes".