Setting up 1P for my wife

I've been using 1P since 2016 and have been an evangelist to those still using post-it notes... However, I am having trouble getting up and going with a family plan. Can someone help me make this easy for my wife and I to start a family plan? 

Background: I have an individual plan that renews annually through Apple App Store. In the 1P help documentation, it tells me to upgrade to Family plan by managing my subscriptions through iTunes or the App store. However this has led me to a dead end, I do not have iTunes on my PC, and in the App Store it only gives me the option to choose between monthly or annual individual plans. What am I doing wrong? 

This also raises a second question - is there any advantages to using Family plan if it is just me and my wife? Would it be easier for her to just manage an individual plan by herself? 

Thanks everyone :)