OK, it's quite easy.
First - DO NOT try to undo the screw marked A, it's tongued to fit the groove in the piston (mine shown removed after disassembly).
Remove the dies from the piston and the base (white and green items in the pic below).
Invert the press and support the platform over the edge of a bench or similar.
Use a brass drift, dowel or other suitable tool to drive item No 2 down in the direction of the red arrow and remove it.
Turn the press to upright and screw the piston (No 3) down until it disengages from the screw, you can then jiggle it out of the press.
You can then remove the groove screw and any other parts you wish to clean and lubricate.
Assembly is just the reverse, the base die holder can be pressed in last of all.
Screw No 4 is used to tighten the cylinder to keep the piston nice and centred, just tighten it enough to remove any side play.
Now that I have mine apart I'll give it a clean and lubricate :lol:
Hope this helps.
Cheers
Jim.