There is actually nothing special to do when creating a template campaign! Simply create a campaign as normal, and populate with your stats, abilities, etc. Then, you will be able to clone this campaign data to any of your new campaigns to get up and running much faster.
You can also check out our #campaign-templates channel on Discord to see if someone has a template you can join and use. We are looking into a user-driven template catalog for the future where you can go and clone campaigns that users are maintaining and offering to the public, but we do not have a set schedule for this feature.