Battery Stuck in Nikon d3100

I'm new to the fancy camera world, and I purchased my d3100 a few weeks ago. I'm going to a gallery party tomorrow, and the battery is half gone so I wanted to charge it before I left but it won't come out. Is there something special I'm supposed to do? Please help! Thanks!

Added (1). What yellow button?

I don't know what you did but just click the yellow button aside gently the battery will pop out if this doesn't work out push the battery gently in and it will follow a spring motion and pop out if still not coming out push it in completely in and try first step and if nothing works go to a hardware store or nikon service center or the place u brought it

Page 15 in your user manual shows how to remove the battery from the camera.

It should just fall out once you open the battery access door and place the camera in the shooting position. It may not fall all the way out, but enough to be able to grasp it with your fingers and pull it out.

There have been reports of generic batteries getting stuck because they are slightly larger than the one produced by Nikon.