Can't rename font

I’m new to Glphys and having trouble renaming a font I downloaded. I keep getting this error message. Anybody have a fix?

You need to save as a .glyphs file. .ttf file can only be imported or exported.

Just did that, thank you. How do I convert it back to a .ttf file so I can add to the Font Book? I tried exporting with these settings and clicking Next, but nothing happened.

Did no font file pop up in Documents?

I tried it again a few more times and it worked. Thank you both for your help.