4 family members want separate accounts
HHow do 4 family members set up separate iTunes accounts so we can all play music but still share purchases?
You can create a new account via a computer's iTunes e.g. Set up an Apple ID in iTunes - Apple Support
The page that you posted from tells you how to create a child account
Then add the accounts to your family share - the organiser has to have a valid payment on their account as he/she takes responsibility for all the members purchases (members can use a balance on their own account, but not a card).
Only iTunes purchases are included in sharing (those still in the store and not hidden from the cloud), your own music (e.g. copied from CDs won't show in the cloud)
Set up sharing : Set up Family Sharing - Apple Support