Have a friend help! Actually the easiest may be to unscrew the front portion of the inner fender liner and have someone hold it open to expose the inner fender area where the filter is mounted.
The trouble your currently experiencing is the main reason I won't ever purchase another in-fender CAI system. They are too much of a pain in the butt to install and service. The extremely minimal gains an in-fender system provides or a standard CAI just isn't worth the hassle.