How setup "iPhone" USB Network interface

My Mac" Mac mini (late 2014), 2.8 GHz Core I5, 16 GB 1600 MHZ DDR3, Intel iris 1536 MB, 998 GB available storage. I was told to use iTunes to upgrade to IOS 12 because I was having problems with the simple method.

I do not use iTunes on a regular basis so it has not been setup but it has been loaded so I used the lighting cable to connect iPhone to Mac and clicked on iTunes and get the following message

My system is unused storage is 998GB My problem is that because of a problem upgrading IOS, mac help told me to use iTunes which I have not used for a long time. After connecting the mac using the lighting cable and clicking iTunes I get this Message.

then when I transfer to Network Preferences I get

What action to keep USB happy ?