To get into the exact spot of footage, in the control panel below the composition screen there is a tab showing time. On double clicking the tab, it will open a window where you can adjust the time and you can reach to the exact spot of the footage.
Motion sketch is a path you want your object and picture to drop or move. For motion sketch, click on the window tab in menu bar and select Motion Sketch option from the window bar. Now you can draw the path and make your image move accordingly.
The file extension for, Adobe After effects project is .aep.