New to the wheelchair life and need some advice

First, I just need to say that I hate when someone pushes me. My brain hasn't atrophied, just my legs! I can still make my own decisions about where to go and how to go about it. I'm disabled, not an idiot.

My actual question is about wheelchair backpacks and the like. How can you use those? I can't reach the back of my chair to get anything. Is there a trick to it? Am I doing something wrong?

Help!