When I download a font I get a file that opens with notepad. I just want to download ttf files, how do I do that?

Look at the icons of the files in the download .zip. If the icon looks like two overlapping capital letters T, it's a font. If it looks like a stenographer's pad, it's a text document. Text documents open with Notepad. Font files don't, unless you right-click the font file, and select Open with -> Notepad.

Could you explain clearly with maximum detail how you proceed to your download ?