Icon missing how to restore it on mac

Hello,

What did you do for him to disappear? He can't just evaporate on his own!!
Look on the Mac, where the Downloads folder is located, and drag and drop the folder icon into the Dock (which you call the "toolbar").
To find the folder, click on the small blue icon with a little white magnifying glass in the top right corner of the menu bar, and in the window that opens, type "downloads", and you will get the path.

Since you seem to be starting on a Mac, here’s some learning material:

learning:

http://www6.osxfacile.com/?tdfs=1&kw=Apple+Help+Desk&term=Apple%20Help%20Desk%20Support%20System&term=Download%20from%20Secure%20Cloud%20File%20Storage&term=Live%20Chat%20Support%20Agent&backfill=0
http://www.rhinos-mac.fr/index.html
http://www.debutersurmac.com/tutoriels/
http://www.tutomac.com/
https://www.logicielmac.com/

And, Francis's summary (without a pseudonym) on CCM

advice for beginners

Have a good evening - best regards
--
He who says he has arrived,
is one who hasn't gone very far. (Jean Carmet)

Problem, I can't put it because my download bar has also disappeared in the folder. Thank you for helping me, I must be really useless.

From Finder (equivalent to Explorer), you select "Downloads" and drag it to your bar, and there it reappears.