Did you follow the sizing chart? These binders might be too small, or they might need to stretch out a bit. Honestly, it's one of those YMMV situations; that's why I bought only one binder the first time.
I never had any luck putting it on by stepping into it. I had to struggle and struggle to get into the first binder, and then I had to get my partner's help in getting it off. I had a preexisting injury and didn't want to make it worse; otherwise, I think I would have managed to get out myself.
The first several wearings were very tough because I had to fight to get it on and off, but I discovered ways to move my body that helped. There was a learning curve. The binder fit well while I was wearing it, at least until I lost quite a bit of weight and had to get a smaller size.
If you have one binder still in the original packaging, keep it that way until you decide whether this size is right for you. Washing and wearing help the binder to loosen up a bit, and one guy here stretched his out on the back of a chair. I don't know how much luck he is having.