Need help with a begginers thing

[k0ck3n]

I wounder if you guys can help me with what looks like a basic thing (did not find any other thread about it)

I needed to change brakerotors on my car, and then I discovered that on my driveshaft the rubberseals are damaged (probebly the wrong name, but look on the picture and se what I mean).

So I removed the driveshafts and order new parts, but now and don't know how to remove the gear (big metallthing on the end so I can put on a the new part. Do have to remove the gear in the other end (gearbox end) or am I missing something here?