π§ Where is the non-SRD Content?
Only content within the D&D 5e SRD can be freely distributed and included in the system. You can view the SRD here: https://tinyurl.com/WotC-SRD
Anything outside of the SRD needs to be brought into Foundry. There are a few ways to accomplish this:
Current and planned modules are available here #dnd5e message
2) Create the class features/items/monsters yourself. This might sound daunting, but once you get the hang of Foundry it's pretty simple and easy. Especially since you can drag-and-drop features from existing content from the SRD compendiums! This greatly helps to give you a good understanding of how the features work in Foundry.
For PCs alaustin has created a playlist of videos to guide you through creating Class Features, Class and Subclass items, and best practices on where to store them:
https://tinyurl.com/alaustindnd5e
We recommended that if you take this approach, only create things as you need them to keep things quick and simple. For example, only create the features for the subclass your players are choosing, rather than trying to complete all subclasses at once.
3) If you have access to the content on D&D Beyond, you can use the D&DBeyond Importer module. The biggest downside to this approach is that it is easier to get confused about how exactly the features work within Foundry since the work has been done for you, but it's really down to how much you prioritize your time vs your money. See Section G below, for more information.
2.5) There are also several statblock import modules that you can use such as 5e Statblock Importer, and Content Parser