[Pisces]

Originally Posted by scott_c2911

I think you can only have one campaign mod enabled at a time. You start the campaign by opening the career option and start a new career.
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Originally Posted by Lord_magerius

You would start a new career for the campaign to work.

The first is true, the second is not entirely true. It applies to all campaign careers that you currently have running (not dead/ended by capture/whatever). Changing those campaign files mid-patrol is obviously a bad idea for the ones you actively play. So starting a new campaign (effectively a new patrol) is the proper way, but it is not restricted to them. So be careful if you want to alternate between commanders.

Originally Posted by Ham920

Thanks for your reply. Let me make sure I understand what you're saying. I can drop a campaign I downloaded from Subsim into the campaign folder and then access it from the career option when I begin a new career?

There is no selection. There is only one you can play. Overwriting the files in the campaign folder voids the older campaign. As already stated, with possibly nasty effect for other running careers.

Make sure you replace the campaigns through using JSGME (perhaps you might need to make your own mod-folderstructure). That way the older campaigns are kept as a backup when you enable the mod, and will be reverted when disabling it.