Bindings are designed to be snug.  Do not try your bindings on dry.  First, dunk the board in the water to get the bindings wet, then squirt some lubricant on to the rubber.  Always use water soluble and bio-degradable lubes. Don't use anything with oil that may break down the rubber, harm the environment, or not rinse out once you have your feet in. Work the lube around in the binding with your hand a bit if you want. It should make your feet slide in pretty easily. 

Once your feet are in and you're in the water, shake your feet around a bit to dispel the excess lube. You don't want to slide out as easily as you got in. All bindings will loosen up after some use. They are tightest when they are new.

You know that the bindings are a little too tight if, after wearing them for a while, your feet become numb. If that's the case, you should try loosening up the overlays. If they are still too tight, return them for a larger size. Most of our bindings come in a variety of sizes.

You don't want your feet coming out except in a pretty hard fall. Similar to snowboard bindings, it's better to be in than out.