Cageym,

When you click on "My Account" there's a picture of my card in the first column on the left, with a number of options underneath.

There's a link that says "View Current APR".  Right under that is a "More Account Options" link.  Click on the "More Account Options" link and there will be a pop up.  

In the pop up, the 2nd column is "Account Management" and the last option in that column is "Increase Line of Credit".

Good luck!