Just wanted to follow up on this post and make sure that you're ok on the files front in Podio.
As Sara is pointing at, Podio is designed to work a bit differently with files. We think of a folder for files as an app item. So if you have a projects app you create an item for your project, in which you attach the relevant documents for the project.
When you need to get an overview of all the files you have attached in your entire workspace you can go to the workspace homepage, click the wrench just above the Invite button, and choose Workspace Files. Here you'll see all the files attached to your workspace and you can filter for relevancy.
We will not see folders in the traditional sense in Podio, but we do have a files app in which you can also store all your files if you like. You can find this here https://podio.com/market/apps/295-files-library