Look at the pics above there shoved into one but there 4 different screen shots of my phone. I think the problem you have is you dont have "device" selected on your screen after the App loads. For example, Look at the top right pic where you see the 8 different small window camera shots, to the far right you will see the word "device" with the 4 squares and red circle.. Yours probably read something differnt. Tap on that and see if you can get it to read "device". Once there, look for the word "group" in the bottom left section of the small camera thumbnails like in the pic above.
AT the bottom half of the pic you see blocks that say "live" Motion" Device settings".. Once you find the word "group" and select it (which is the group of cameras your using). then you can tap "device settings" (bottom square).
Look at the Bottom right pic.. One of your group cameras will be at the top center with 2 read arrows like what mine is above in the pic. Use the arrows to select the camera you want to adjust.
On that same screen look for the square that says "detection area" tap it, and another screen will come up where you can adjust the area where you want the camera to set motion alerts, once done with that you can select "save" in the top right to save your setting for that one camera. Once completed, just repeat the process for the rest of the cameras you have.
This is with the MeShare app on Android.