1st. go to this webpage "https://files.minecraftforge.net/net/minecraftforge/forge/".
Downlad the Forge version for your minecraft version. Place the jar file on yout Desktop, doubble click it and let forge do his install work.
you should see a pop up that forge has finsihed and downloaded several libs, blah, blah. Klick okay and the Forge Modloader is done.
Now open the Minecraft Launcher...at the top you see several Tabs; Play /Installation/Skins/Patch Notes... klick on "Installation".
This is one way to do it:
1) Klick: New Installation. 2) Name your Intallation like ( 1.16.5_36.1.32) for example. so you know which MC Version/Forge Version.
3:) In the next Field the "Version" Dropdown Menue choose the version you just installed, there should be an Entrance called: "release 1.16.5-forge-36.1.32" choose this.
4) Game Directory: If you use the "default directory" klick on Browse and pay close attention to the default Minecraft directory... you see it?
5) leave the rest unintended (only needs to be modified if case you place your mc game dir to a different location). Hit "create".
6) The launcher jumps back to the play Tab and you see your newly crated mc imstance.
If everything went okay klick play and MC should start! In the lower left corner there should be written whiich Forger version/modloader. Dont create a world do nothing, simply close Minecraft.
7) You remember the path??? C:\user\username\AppData\Roaming\.minecraft\! You need to enable "hidden elements/files/folder" in your Explorer window. There are easy tuts all over the net.
Inside the minecraft folder you should see a Folder called "mods". This is the place where you copy your downloaded mods.
To remember: This is the base on how to install Forge Modloader, it doen´t fit to facric modloader procedure.
I hope there is some essential help for you.