Adding email addresses to W10 Mail App.

I have just resurrected an old W10 version 1909 machine for a family member to use for email and browsing. I set up the Mail App for email and she can receive, send and reply to emails just fine. However, if she tries to send a new email she has to type in the complete address in the To field -- cumbersome and prone to typing errors. Is there a way I can set up an address book for a dozen or so different address to avoid this annoyance? My guess it has to with the People app but that is only a SWAG.

Will someone please guide me through the process to get the Mail App to behave like I would like it to?

Thank you very much

Bastet said:

Double check under the mail account - settings>Click on the account>Change settings> turn on contacts - to see if Contacts (& calendar) is active, this will add any contacts already on the account to the list, if there isn’t any contacts under the account then you can add them manually within the People app by clicking on the + icon.

That was easy enough! Thank you.