Can a Macintosh person tell us how to change the name of a file?

Can a Macintosh person tell us how to change the name of a file?

I don't know anything about changing names of files on Macintosh!

Today I asked an emergency question on the rec.autos.tech newsgroup (the
question is below) which has an MP4 uploaded to a web style forum which
only accepts small PDFs (less than 12MB).

I easily used Windows Shotcut freeware to convert the ~50 MB MP4 video to
just ~5MB (simply by changing the pixels to 640x480) and then uploaded the
much smaller files "as a fake PDF" by changing the name from file.mp4 to
file.mp4.pdf instead.

The Windows users had no problem changing the name but all the Macintosh
users complained they can't change the name and I can't tell them HOW to
change the name. It's really important that I get these Macintosh users to
hear the file!

Can a Macintosh person tell us how to change the name of a file?
Whatever you write, I will cut and paste into the web forum thread.!

Thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

================================================== ===============
Here is the original post to the rec.autos.tech newsgroup
https://groups.google.com/forum/#!forum/rec.autos.tech
================================================== ===============
https://groups.google.com/d/msg/rec.autos.tech/uicX1l6oO_U/zzAfaVfSBQAJ
Subject: Have you ever heard THIS SOUND inside your engine?
URL: http://www.bimmerfest.com/forums/showthread.php?t=1181089

Nobody on Bimmerfest knows what is causing this noise and I can't use the
car until I figure out how to figure out what the noise is.

This only started after I did some work this weekend on the valve cover but
it sounds like someone left a socket inside the engine and it's bouncing
around somewhere.

I'm pretty sure I didn't leave anything inside where this sounds like it's
in the intake manifold but it's hard to figure out where it's coming from
as it's intermittent.

It sounds like it's coming from the top of the engine somehow but it's hard
to place where.

You should not need a login to read that thread and download the videos.
http://www.bimmerfest.com/forums/attachment.php?attachmentid=730369&d=1513035084

Here's just an audio file:
http://www.bimmerfest.com/forums/attachment.php?attachmentid=730353&d=1513034666

When you download them, remove the *pdf which I added so that the MP4 would
look like a PDF to the forum upload GUI.

I can't imagine what is making that noise which is why I'm asking you for
how to debug that noise. Thanks!