Are you wanting to take out the whole tension and replace it or just the tension post? You can remove the whole thing by finding a set screw on one side or the top of the machine near the tension - some will be a flat screw and I have seen some you will need an Allen wrench - more likely a little flat. You will likely have to look inside the nose cover above or to the left of the tension. I have also seen a few on the right accessed through a hole next to the tension. Once you pull out the set screw the whole thing should pull out. I have a machine someone ruined by forcing the little cup out - it broke inside the machine and there are a million pieces of metal inside there. If you want to just remove the tension post it varies according to tension. The older Singers are threaded on the end and will just unscrew. Some have a set screw on the little cup that holds it in the machine. You may have to pull the little cup to get the set screw for the post out anyway.