Resources in Teamwork Cloud (TWCloud) include projects and documents. Resource Manager and Resource Contributor roles enable users to work on document resources.
One of the goals of TWCloud is to allow multiple users across different locations to access the same resource (project or document) and work on it concurrently. To accomplish this, you must import files to the server first and then open them on Teamwork Cloud Admin (TWCloud Admin). Resources listed on the Resource application in TWCloud Admin are either newly created or imported ones. With the resource management capability, you can assign resources to users, monitor progress, and edit resource properties, as well as rename and edit their categories.
You can import a resource to a specific category or you may import it first and create a category for that project/document later.
About the Resources application and TWCloud Admin combined features you can read here.