I don't like this game, it's too difficult for me so I won't be coming here anymore. I'm just being honest, I'm only sticking with games that I'm good at.
For level creation tips, feel free to read this guide for the several games on the site. Don't worry about getting your levels rejected, everybody started like that.
If you rather play the games and levels, there's not much to tell you actually. Play the games you like most, maybe all, and play the official levels first. They are a great introduction and get progressively harder.
Practice makes perfect, so you might need to play the games a bit more to become good at them. This also goes for creating levels.
It would be nice if you would rate levels, as this is an easy feedback for the creator. It also rewards you with a small amount of experience points.
That's something for new people. When you are new at making levels your first few levels are not that good so JP imposed a limit in the first month so hopefully you spend more time improving your levels that way.