How to install smartApp on child device?

Hello, I am playing with smartthings and I cannot figure out how to install smartApp on child device.

So far I just randomly choose one device template and made one simple service manager that only get and add child device.

So, I installed service manager on my smartThings mobile application and tried to get the child. I see the child device is register on my “thing” window, but if I click that device, there are 3 tabs( right now, recently and SmartApps) if I go into smartApps, I don’t see any installed smartApps.

I thought If I can get and add child device by using add/getChildDevice api then I though my service manager gets installed automatically? is this right? if then why i am not seeing my smartApp installed on the device?