It's a grey app with gears on it. You'll likely find it on the Home Screen.

Before erasing and restoring with iCloud, you may want to make sure you have an iCloud backup first. To do so, tap the Apple ID name at the top of the "Settings" page, tap iCloud, and scroll down and tap iCloud Backup. As long as there's a backup date listed here, you can restore an iCloud backup.
 It's near the bottom of the screen.

If you checked for a backup, first tap the "Back" button in the top-left corner of the screen.
 This option is at the bottom of the General page., You'll see this button near the top of the page., This is the code you use to unlock your iPhone.

If you don't have a passcode, skip this step.
 It's at the bottom of the screen., This process will take a few minutes. Once it finishes, you'll be able to select an iCloud backup., It's the circular button below your iPhone's screen., To do so, select a language and region, then choose a Wi-Fi network to connect to., This option will allow you to select and install a backup from your iCloud account., These must be the same credentials you use to download music or apps., It's in the middle of the screen., Remember, the date you select must be from a time at which your desired texts were still on your iPhone., Once the restore is complete, you should be able to view your previously deleted texts in the Messages app.
Open your iPhone's Settings.
Scroll down and tap General.
Scroll down and tap Reset.
Tap Erase All Content and Settings.
Type in your iPhone's passcode.
Tap Erase iPhone twice.
Wait for your iPhone to finish erasing.
Press your iPhone's Home button.
Complete your iPhone's initial setup steps.
Tap Restore from iCloud Backup when prompted.
Enter your Apple ID email address and password.
Tap Choose Backup.
Tap a backup date.
Wait for your restore to finish.
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