The process for deleting files, folders, and projects is nearly identical. The only difference is what page you're on to start the process.
To delete a project, you'll need to look at the project list.
To delete a folder, you'll need to view the root of the project, or whichever folder contains the folder you want to delete.
To delete a file, navigate to the project or folder that contains that file.
The process
Start by navigating to the appropriate page where you see the list of projects, folders, or files that you want to delete.
Then, click the three vertical dots to the right of the item you want to delete:
In the menu that pops up, select "Delete":
Last but not least, confirm the deletion when asked. Remember, this is permanent:
As above, the process is nearly identical for files, folders, and projects. The only thing that changes is where you go to delete the item.