How to upload configuration to Fortigate from console?

Newbie here who has gotten myself in trouble. We have 2 Fortigate' s, a 200-A (in production) and a 200A-HD (offline) both on MR6 P3. My ultimate goal is to use the extra offline unit to get it upgraded to MR7 P5, test it and swap the units so the other unit can also be upgraded to the same level. Both units have simple configurations with minimal FW policies using VIPs to translate internal to public IPs. As my first step, I saved the configuration on the production unit and loaded it into the offline unit but then could not access the offline unit anymore using Web access. Using the console, I could see that even the name and serial numbers were copied to the new unit so I think perhaps the header values should have been edited first. I was able to use the CLI and hyperterm to change the internal and wan1 IP' s to be different from the production one. However, my problem now is that I cannot access it from either the WAN or the internal side using a browser. My only access is by the console and CLI of which I have used very little. There are no trustedhost settings on the admin login so I am lost as to why I suddenly cannot access the unit from either port? My question - Is there a way to upload a new configuration file using the CLI? Can the USB port used for this? (a FortiUSB was mentioned in the KB but not much else and does not appear to be a standard USB device). Or would it be easier to set it to factory defaults and start over that way? I want to try editing the header values in the config file before loading into the second unit in case that is related to the problem. Is this something that I need to just get support on the phone to help me? :) Any assistance would be appreciated along with any advice on how best to copy the config from one unit to another. They are both currently on the same FW revision. Thanks so much.