how do I get an apple Id for the first time for my Iphone 8+?

You enter your Apple ID choice and the related password choice when you Set up your iPhone, iPad, or iPod touch https://support.apple.com/en-us/HT202033

You used an ID to sign into the support community.

See the Apple Support article(s) below.

Apple ID - create a new.      

Apple ID – Create        

Apple ID - Could Not Create or Could Not Set Up iCloud message.