1 & 2 are the same. The forward or reverse commands start the spindle.
Unfortunately, you can't do both with this board, as there's only one relay. See this image.
http://www.omc-stepperonline.com/ima...d-st-v2_01.jpg
The terminals marked "Spindle On/Off Control Interface" are controlled by the relay, and go to the FWD terminal on the VFD.
The terminals marked 0-10V spindle speed go to the VI and DCM terminals. Look at the bottom of the board, for terminal information.
Assign Pin #1 in Mach3 to the PWM signal.