You can switch coord systems a couple of ways - use the MDI and simply type in G54, G55...etc. then hit enter, note that the display will change from G53 to G54 accordingly, or use F8 (Choose Coordinate) and choose G54 through G59 there. If the display is still showing G53 as active, then you are sill in machine coordinates. The display will show G54 when you are properly in the work coordinate system.
To zero your work coordinates, you must first choose a work coordinate system (use either of the previously described methods, MDI or F8), then choose F7 (Set Coordinates), choose the axis of choice (XYZAB, etc), and enter zero then enter. You can enter any value you choose for your work coord as long as its within the axis' travel limits. If not, the control will give a soft-limit error.
To home an axis, press reference, then the axis of choice (XYZAB) or 0 for all axes. This assumes that you have properly setup your axis homing parameters.
FYI, I am about 18 months into an SZGH 5-Axis 1000MDC retrofit coming from Mach 3. I absolutely love the control, it simply works every time. It has never crashed in 18 months or had any issues not caused by me. Also, Mike Bond Huang at SZGH is a God send for support. Reach him at engineer@szghauto.com. He has helped me tremendously. I took a leap of faith buying the SZGH as there was not much internet support or info available. I'm glad I did. I have a good grasp of it now, and will help you as I can. You may also search "Newker" control for support online. SZGH is simply a private label brand of Newker controls.
Also, please keep posting here, rather than DM'ing so that future users can access the thread details. Happy to help as needed, and good luck on your control. You won't be disappointed once you have it tuned. Mine still makes me smile every time I rigid tap (not easy to do in Mach 3).