I have a shape layer as a circle and i want to have it slowly convert into a rectangle and i don't know how! someone please help!
Create a circle. Convert it to a Bezier path. (You can convert a parametric path to a Bezier path by context-clicking (right-clicking or Control-clicking on Mac OS) the property group for the parametric path and choosing the Convert To Bezier Path command from the context menu.) Set a keyframe for the path parameter. Move forward in time. Change that path to a square.
Wheres the property group?
Twirl down the parameters of your shape layer.
Also, go through some basic training tutorials on AE and, specifically, shape layers. You can find that in some of the links here: Getting started with After Effects