Removing Menu Items & Changing Icons

Hi there, I am looking at removing some of the menu items such as "live meeting" and "Instructor Led Trainings" as I do not wish to use these features currently. I cannot seem to be able to remove these when editing the menus as it seems I am only able to edit the main menu navigation? Furthermore, I was wondering if there was a way to replace the main menu icons with my own specific icons? Such as my own home icon. Can all this be done in the override CSS or will I need to make my own custom sub theme? Thank you in advance!