Let's start with a few standard definitions just to get on the same page.
N/O = Normally Open Contacts, actuate the switch to Close the Contacts
N/C = Normally Closed Contacts, actuate the switch to Open the Contacts.
Terminal = the screw you hook the wires to, like on the switch or VFD terminal block
Contacts = the switch contacts, the actual switch inside the Contact Block on the switch.
Contactor = a large relay normally used for heavy power loads or motor starting.
A light switch in a house is usually considered a N/O switch, when you actuate the switch the Contacts Close and the light turns on.
DCM is the common, it should be wired through the N/C Stop Button Contacts, then to one side of the For/Rev N/O contact terminal and one side of the Start switch N/O contact terminal. The other side of the For/Rev and Start switch should be wired to the proper terminals on the VFD terminal block.
The Stop button should be a Maintained Position switch. Think light switch again, you flip the switch and the light stays on until you turn the switch Off again. The Starter switch in you car is a Momentary Contact switch, it springs back when you release the key after starting. I think the VFD can be setup to accept a Momentary Position switch for the start terminal.
Take a look at this thread
http://www.hobby-machinist.com/threads/huanyang-vfd-wiring-setup-vfd-newbie.34107/
Below is a wiring diagram just for ease of reference later