O.k. when you join a GB you will build together, there is no judging on whose done the best job. Usually the badge is on the first page before the build starts, sometimes you are not allowed to use it until your build is complete, or the build is over. In order to put your badge in your sig. you will need a hosting site, I use www.photobucket.com it is free and works well for me. You have to upload your image, copy the IMG code and paste it in to you sig. area.
Hope this helps, Anthony.