I think lotek has a good suggestion. To start with loosen up the straps to make slipping your feet in easier. Once you get the hang of it, then you can tighten them. I like them, they hold your feet to the pedals, but give you a little leeway on foot position.

As Lem said, there is a little art to it. And several ways to do it.

You can put one foot in the clip before starting, and then give yourself a power stroke and while coasting, flip the other pedal up by sliding your foot backwards on the little tab on the bottom of the pedal and sliding your foot forward as the clip comes over and around. Or you can just get started with your foot on the bottom of the pedal and give a push, then slip your other foot in the clip
, and push again, and slip your first foot in the clip. It takes a little getting used to, but in a couple of days, you should be comfortable.

And I've heard it said, that in cases of accident your feet shrink making it easy to get them out of the clips. ;o)