Make sure you have Mach configured for Safe Z, its from Config menu.
I prefer to use SafeZ as Machine coords, that means I always know exactly where it will go. Z0 in machine coords should be fully up and all Z moves from there are down and negative. So if you set Safe Z as machine coords 0 or -.5 or similar then Z will always raise to that point when doing RFH or Go To Zeros.
You can also set safe Z as an incremental move or work coords move but as said I think machine coords is preferable.
Anyway, RFH, it will only work if licenced, I believe you are so thats fine.
To do RFH you select the line of code you wish to start at, you can do it by scrolling through the code window or selecting a line, doesnt matter.
Once you have chosen where you want to restart you press RFH and Mach will run through the code and then tell you to press Start when it has finished running through it. You press Start and then a prep move box will open, check the coords look fine and you can then press OK, Mach will move to the position detailed in that box but will observe Safe Z, ie it will raise first, move X and Y then lower Z. Once that has happened you can then again press Start and it will continue.
Few things, best to select a start that has Z above the material if possible.
If you have an ATC or use height offsets it is best to start at a tool change or make sure you have the correct tool and height offset loded by MDIing it prior to the RFH.
The prep move box has an option to Start Spindle, you need that chosen. Also you need to have a value in the spindle speed DRO as the spindle will only get a M3 command and no Speed command.
Hood