How to save the image on the device in order to use it in the database

I have an application that works on the same principle as a contact book in android. I take an image from the gallery to assign to the contact, but I don’t know how to save it correctly. So that it is stored locally in the application, and could be used at any time. For example, when your friend calls you, you see a notification in which there is his photo, number and name. My application, the application also works, but I don’t know how to save correctly the photos that users will assign to friend profiles. I am using ROOM. Someone explain in detail how to use it and save the photo correctly.