Do you want to have multiple accounts associated with this device or be able to view, respond and send emails from multiple accounts on one device in one app?
I'll assume the latter...
In the default mail app, simply called "Mail", not to be confused with GMail, both of which usually come installed on Android devices, both of which usually assume your Gmail mail from your initial log in on the device. Find Mail in your app drawer, open the app and touch the 3 dots in the upper right corner. There you will see the option to add accounts. It will mostly do everything for you when adding accounts from any of the big email offerers, Yahoo, Google, AOL, possibly even spectrum or the other cable companies these days but for newer, smaller or lesser known providers you may have to do a little online research.
For the mainstream offerers you'll just pick a category, if you don't see your offerer listed it's a good choice to pick PoP, enter your email and password and you're done.
If you don't have the stock Android app there are several at the Play Store that will do this, Maildroid, K9 and several others are highly rated.
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