Hey there!
It sounds like you're interested in wanting to know how you could add photo overlays and stickers onto your photos that you've taken with your iPhone. I would recommend you try searching the app store for apps that allow you to do things like that. You could try searching "Stickers for Photos" to start, and see what apps you find from there.
For now though, unfortunately there is no built in feature of iOS that allows you to directly add stickers or overlays from the Photos app that came pre-installed on your iPhone.
Hopefully this helps to answer your question!
🙂