as o much i know i guide , i m not good in animation and one more thingh ps is only a small and simple way to simple animation ,there are many limitation ......
all wht do that ...... first copy the layer by ctrl+j ..... and got o windows pannel and click animation on that ......... point to be kept in mind u want to make frames ..... and in each frame u do the changes u want and yes u need to hide the previous layer to animate ........ try this u understand by keep practising