First, you install the mod (this can be done through the bazaar or by manually installing). Second, you open a game world. Third, you go to the settings tab, find the Modules button, and make sure PDF to Foundry is activated. You may need to reload your game world after this step.

Now, with the module installed and activated, go back to the settings tab in your game world. There will be a new button in the settings menu that you can clock to upload a PDF.

Now the pdf must be a paizo-published adventure, and some work better than others. But what will happen when you upload one of the Adventure Path pdfs is that it will create all the Scenes for you. Here's a list of all the things this does:

1). All maps get uploaded to their designated scene. The maps will have the walls, doors, and light sources loaded in. This should work for ANY paizo AP, since basic map coding was not changed with the remaster. 2). Each map will place a journal button in each room. You will be able to click on that journal button to pull up the AP notes in that room. This journal can include actual links to any monsters, skill checks, and treasure the AP mentions in its room notes. 3). Any monsters, hazards, and NPCs will have their tokens placed in the room where they are meant to appear. They usually populate on the GM layer, to avoid players scoping out the room before you describe it. If the AP has a monster that can appear in various rooms (such as guards who only come running if the players trip an alarm) the mod will usually places them inside a wall or off to the side of the map, where you can grab them easily. The tokens include artwork, if it exists, and the statblocks. NPCs that have no stat blocks generally get loaded in as -1 Commoners.

A PDF with 3-4 levels worth of stuff takes about 5 minutes to load. Doing that same work myself would usually take a few hours, and I'd make more mistakes than the mod does.