From that Popup Window, you should see a Plus Sign Icon- to Add new items to the panel.
If you click that, a popover Window opens with a list of Pulgins you can install.
If you need, you can run this in terminal to install more
sudo apt install xfce4-goodies
See if Battery Monitor is listed and if so, Add It to the panel and check if it can read your Upower Output and display the battery percentage. Some users prefer it over the Default XFCE4Power Manager Plugin.
No need to apologize, you are not a pain. It was not very long ago I migrated from Windows to Linux and was learning all of this. But for now, I keep getting called away from work- So, I need to go away for a while. If I do not respond right away, I probably was crushed under a pile of metal or something.