Hey rosemaryfromgreenwich,
If I understand correctly, you do not see the Messages icon on your Home Screen. It could be that the app has been moved inside of a folder. One thing you can do is swipe down on the Home Screen and search for the app. Another thing you can do is Reset the Home Screen Layout, this would put the apps the way they were when it had factory settings.
Use Search on your iPhone, iPad, or iPod touch
Tap Settings > General > Reset
How to erase your iPhone, iPad, or iPod touch
Thank you for using Apple Support Communities. Have a good one.