Sorry for the wait, Warrior cats!!!
OK the cat gives you a message BLAH BLAH BLAH..... Then a cat will appear click scent to scent the mouse, (follow the red lines) then click on were ever the scent leads to. use the right arrow key to move forward and press "space" to unsheath claws. Kill the prey, then a button will appear that says "carry" press it to carry the mouse! (sorry I know it isn't great.