There are three axis x, y and z that your picture can rotate and to select the axis, you have to click on the right side of one of the three boxes that resides right below the “Tool bar”. The “Tool bar” is between the “Source Name” bar and “Parent” bar in the composition panel.
In edit bar, if you select split option you can split your video clip into two sections or layer. So, when you want to do animation separately for each layer or each video clip you have separated, you can do it by using split layer option.
In the composition panel, select rotation option by pressing ‘r’ on your keyboard. Now on the right hand side you will see numbers, which show how much degree you want to rotate the picture. You can rotate the picture by increasing and decreasing those numbers.