Remove the gear plate as a whole. Then your clutch bolts need either a 4 or 5mm hex wrench. If you don't have a piston stop, then you need a way to keep the piston from rotating when you try to loosen the tight as hell clutch bolts. There are 2 ways I did this before I got a piston stop.
1. Put a hex into each of the clutch bolts and use a long wrench or screw driver to brace between them- creating leverage.
2. Use an open ended adjustable (crescent type) wrench and open it pretty wide. Stick it into the clutch housing with the clutch rotated so the pads are straight up and down- leaving enough space to wedge the wrench on the side. This should block the clutch in place and keep the engine from rotating while you try to loosen the bolts.
No matter which one you try, just don't lose the 2 washers or 4 wafer washers that are on these two bolts... then you are screwed.
Also, if the clutch you are tying to put in is for a zennoa and not an HY/CY... then the bolts will not fit through the holes because there is a 1mm difference.