In order to remotely connect to the computers on our office network from outside the network, I had to do the following:
(1) I changed the NoMachine server port to be unique for each machine in our office. For example, I set one machine to port 4221 and one to port 4223 and another to 4225.
(2) In the main router for our office, I had to Port Forward each of those ports to the respective computers local ip address. So if Computer A’s local ip address was 192.168.1.123 and I set its NoMachine server port to 4223, then in the router I would port forward 4223 to 192.168.1.123 port 4223.
After this, I could then access the computers individually from offsite locations.