Keep practicing with them. I find that mine sometimes don't always clip in first time but that's easily done by applying firm pressure on the pedal and it seems to clip in after a bit of a wiggle of my foot
When I first used clipless pedals (about 6 months ago) I managed to fall flat on my face when I stopped because I forgot about having them so didn't un clip
When I first used clipless pedals (about 6 months ago) I managed to fall flat on my face when I stopped because I forgot about having them so didn't un clip