Three ways to get documentation into a project, depending on whether you are adding one file or moving a whole folder structure across.
Using the Upload button
Open Files in your project.
If you want the files to land in a particular folder, select that folder first in the panel on the left. Otherwise it will land in the All Files Folder.
Click Upload at the top right and choose your files.
Uploading starts on its own once you have chosen the files. There is no separate confirm step.
Dragging files in
You can also drag files straight from your desktop onto the file list. Same result, fewer clicks, and useful when you already have the folder open on your computer.
Uploading a whole folder
Files accepts entire folders, not just loose files. Drag a folder in and its structure comes with it, so a "Permits" folder on your machine arrives as a "Permits" folder in the project rather than as a pile of files you then have to sort.
While files are uploading
Each file shows its own progress as it goes.
You can keep working. Browsing and sorting still function while an upload runs.
If an upload is interrupted, it picks up rather than starting the whole file again.
Replacing a file rather than adding a copy
If you are uploading a newer revision of something already in the project, do not upload it as a second file. Open the file's ⋮ menu and choose Upload new version. The file keeps its name and its place, and the old revision stays available in its history. Example: Uploading the most recent version of a schedule. See Preview Files and Use Version History.
Every saved version counts toward the project's storage, which is shown in the Files header.