Aha!

So it works, thank you very much for your guidance, Rascas!

So, for future Googlers who may be having this same issue (Missing the PVR's in Kodi on Retropie), here's the full solution:

Install Retropie, then install Kodi via the "Optional Packages" in the configuration menu.

When you're in Retropie, press F4 on your keyboard to open a Terminal window.

Enter the following commands one at a time (to install the "IPTV Simple PVR"):

apt-cache search kodi-pvr

sudo apt-get install kodi-pvr-iptvsimple

Once complete, type "exit" (without the quotation marks) to get back into Retropie.

Scroll to Ports then choose Kodi.

In Kodi, DO NOT go to PVR's. If you do you will see it is blank and will get angry and think what you did in fact did not work.

Instead, go to "Add-Ons" then "My Add-Ons" and view "All" and you will see the IPTV simple client. Go to it and then Enable it as most likely it will be Disabled to begin with.

Voila!

If you know how to use IPTV then go ahead and set it up.

Take Care!

Can´t find / install PVR IPTV Simple Client