Hey Ryan,
this goes this way. For the switch, a SPST is sufficient. You can use either “normally open” (NO) or “normally closed” (NC) type since this can be set inside the Onefinity Controller. If unsure, you can buy one with both NO and NC, like this one.
There is also much information in this thread.
If you have a setup with a safety relay on your VFD (as shown here), you can also wire it the other way: The Emergency Stop switch is then connected to the safety relay and this stops the spindle at the VFD and this triggers “estop” pin 23 on Onefinity Controller. This would have the advantage that the VFD would also stop the running program on Onefinity Controller in all other error cases the VFD may report.