Basically I started the characters in Princes of the Apocolypse. I purchased the Storm Kings Thunder module and I want to incorporate that content as seemlessly as possible into the existing campaign. Any advice on the best way to do that?
The NPC sheets can be easily transferred over via the Character Vault. The other things (Maps, Handouts) need the Transmogrifier, which is a pro level perk.
I might suggest going the other way, create a game using SKT, and then export your players' characters to it via the vault. It won't quite be seemless, but it'll be pretty close. You can transfer their characters back and forth as needed based on what they are doing.
SKT has a massive amount of content, in most of the feature-categories that Roll20 offers (characters, handouts, pages, rollable tables, and so on). Even with the Transmogrify tool of Roll20 it would be a lot of work to move everything from SKT into another pre-existing campaign. I agree with Scott's suggestion. It's likely easier to move the important bits from your existing campaign (Character journals in particular, using the Character Vault method or Transmogrify), into an SKT installed game.
Thanks all, I am still a bit of a novice with roll20. I was able to use the character vault but I cant seem to find how to access the Transmogrify tool.
Transmogrifier is a Pro perk, you'd have to be subscribed at the pro level to get it (but it is quite awesome and what caused me to take the plunge to pro). At the Plus level, your kind of stuck with creating a new Game based on a Module, and using Character Vault to transfer over.
I've done this recently. Transmogrifier moved the things I wanted to move very easily.