Look down inside the star shaped hole at the top. See the screw ? That's what keeps everything together. The barrel of the winch pulls off when that screw is undone.
N.B. Pull apart slowly and carefully. There are spring loaded pawls which can pop out and disappear overboard ( and spares are hard to get hold of ). Cut a hole in the bottom of cardboard box and pop that over the winch before disassembly to catch any stray parts.
Winches are actually quite simple mechanically and it is easy to reassemble, but take photos if you are worried about getting it all together again.
Wash the parts in Parafin to clean congealed gunk off them then LIGHTLY regrease and reassemble. Don't get grease on the pawl springs. Use a bit of 3-in-1 oil. Don't use WD-40 , it leaves a sticky residue which attracts sand and grit .
I did mine easily enough and I'm a mechanical numpty so don't be scared.