The Quadstick cannot be used directly with an XBox console. It must be connected through a USB adapter, like a
Mayflash Magic-X or a
Brook Wingman XB3, though there are others.
The best settings for most adapters is "Enable Boot in PS4 USB mode" on and "Titan Two PS4 flag"
These were the settings the quadstick was shipped with. Those settings are compatible with the widest variety of adapters.
First person shooters are probably not the best game choice for new users. When the player needs to spend time thinking about their next move, their character will spend a lot of time respawning. A turn based game, or a puzzle solving game that allows plenty of time figure out which hole to sip/puff, or mode to be in, will be less frustrating. Play something like for a week or two, get familiar the concepts and operation of the quadstick, then they will be ready to take on something more demanding.
Minecraft, Lego games, Rocket League, or driving games would be worth looking at.