Gedit is either not installed at all, or not properly installed. If you have another text-editor then just replace "gedit" in the commands, with the name of your text-editor.
If you think you should have Gedit in your system and that it is the text-editor you want to use, then do this. In terminal(without quotes):
"sudo apt-get update && sudo apt-get install --reinstall gedit"
As for usb wifi-adapters, they are a struggle even for more advanced users. No wonder you are struggling. There are lots of dongles that simply doesn't work in linux, at least not out of the box. Are I correct in assuming that the usb wifi issue is solved? If that's the case, so thumbs up. Well done! Patience will get you there. Always