Right now you have to click on the box and choose one of the empty ones (why the hell do i see all of these btw https://puu.sh/wdoN1/2810ddc335.png). To add mons/sets u need to find them in the list of mons (this only becomes marginally easier by typing the name), and then click on the mon and then after that click the sprite in the top left corner to add it. Removing a mon is also a pain because u basically have to start over with a blank team and re-add everything, since you can't directly remove it. This is incredibly annoying and I really think a better system needs to be in place for this tool to be usable, I can't stand to use it because it is so frustrating.