Accidentally deleted the Mail app from the iPhone home screen

Wife was having problems with her phone popping on while in her pocket. Apparently it deleted her email from the Home Screen and no where to be found on her phone.

Went to App Store, it showed the download cloud (so it was off the phone), downloaded and upon opening, it just give you the new app options.

Did some research, peeps were talking about opening "settings> mail and turning something on there but I couldn't find it.

Is this where I have to recover from iCloud backup? I do have a copy of her email on a old phone if there's a strategy there ......

Also, anything we can do to cut out the butt editing?

[Re-Titled by Moderator]