What are fuses used for?

Where do you put the fuse????

If you have the manuals for your equipment it shows you where to replace a fuse. If you don't have the manuals you can probably download them from the manufacturer. 

Thank you very much.

Look on the back panel. Near the AC cord/outlet you will see a round (usually) screw-type cap. Below it will be a designation indicating the size of the fuse required. Unscrew the cap and pull it out. The fuse is held at one end by the cap. It is a press fit. Pull on the fuse to remove it. Hold the fuse up to a light and observe the very thin wire within. If it is intact the fuse is good. If the wire is broken the fuse needs replacement. Replace only with a fuse of the same rating on the back panel.

Some fuse holders are square and require a push-in for release. Others are round and require a push-in with a twist before they can be pulled out.