When adding content in the content area hover over the divider line where you would like to add the content and click on the plus icon to reveal the Add Content menu.
The third option on the Add Content menu is Upload.
When you click on Upload from the add content menu the file manager will open.
From here you can select the file or files you wish to upload.
Once you have selected the files you can click Open to upload them on to the Course Content at the point were you clicked on the add content menu.
Alternatively you can drag and drop the files on to the Course Content at the point where you clicked on the add content menu.
Currently it is not possible to drag and drop folders, although this ability will be coming in the May 2023 update.
The files will appear in the Course Content.
There are a few ways you can Upload files to an Ultra course see our guide Presenting Files to Students for further options.