[Superman]

Some auto parts stores will loan you the gauge set and vacuum pump for free. AutoZone does this in our area.

Lots of videos on this. Watching them will tell you what to do.

But first, checking the fuse is a good idea and visually checking (or listening for) the compressor clutch to engage, are all good ideas. If the clutch is working, then you should have at least cool AC air if not cold air. If not, then your refrigerant has likely leaked out. If you suspect this, then use a 'black light' to see if you can find the leak. This will work IF the refrigerant had the special dye in it. Most common leak places are at the Schrader valves, at the o-ring connections of the hose/tube system, or at the nose seal on the compressor. The leak can be at the compressor nose seal, but more often is at an o-ring or Schrader valve.

If you put refrigerant in, then use the stuff with the special dye. For most of us, putting refrigerant in probably means releasing what is in there first, then fill it with the specified weight of refrigerant for your system. Using a kitchen scale. The oil that is in the system will likely stay there so you don't have to guess at that, but this requires that the system be released very slowly.

Lots of videos on this.