To begin using Pathagoras, you should have, or should create, at least one folder which contains actual forms that you intend to use for document assembly purposes. (A folder which contains documents that you will be converting into forms will also work).
If you do not have a folder in mind, then create one. Navigate to the location where you want the folder to be. Its location is not critical right now. You might want to call this new folder "Pathagoras Forms" just to identify it as 'special' while you go through the initial exercises.
Whether you are using an existing folder or have created a new one, pour 'lots' of forms or documents into it. Put in whatever relates to the subject matter. (Don't worry about getting all documents and forms into folder right now. You can always add more later.) Populating the folder with 'lots' of documents is more important at this stage than even having 'well-Pathagorized' documents.
Note: Creating folders and sub-folders, and moving documents into them, are standard Windows and Word activities. Use the "copy, cut and paste" and "drag and drop" techniques that you already know to move documents into the folder.
Pathagoras does best with lots of documents in a single folder. It is better (and easier) to have dozens of documents in one or two folders than to have one or two documents in dozens of folders.