How do you delete a download off an Android tablet?

It probably varies by phone, but in my Apps there is one simply called Downloads.

I see a list of files, and when I select an item a trash can icon appears.

Otherwise, you can install a File Manager and browse through folders like on a computer. I’ve used ES File Explorer in the past and it will do the job, but I don’t recommend it, it’s gotten bloated and intrusive with pop ups.

This one looks OK, I just installed it
File Manager by Asus

I found it in this list:
10 Best Android File Explorer Apps

What @Call_Me_Jay wrote, plus what I really tend to do is plug it into a computer with USB cable, say yes/allow on the dialog that comes up asking if I want to allow file access, and then use a file explorer program on the computer to mess with the files on the tablet.