How do I add an app back to my home screen on my S21

[userQNccDYGM8y]

I recently inadvertently enabled a function that added the massaging app to my home screen and was able to open up a mini window showing messages. You could tap near the top of the window to enable some other options such as enlarging to full screen or close. 

Well I somehow deleted the app on the home screen and cannot figure out how to get it back. 

Can anyone help? Thanks 

[user365170tdJ15 · Accepted solution]

On an empty screen , swipe up to show all apps screen, find the app you want , then long press to show its menu , then choose "add to home" option
... see screenshot - I highlighted
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