Yeah it is possible for sure. You will need a 3.5mm to rca cable. Some amps also have a 3,5 mm aux in but that is rare. But you will definitely be alright to just buy a 3.5 to rca cable and plug the rca side to the amp input and 3.5 side to your phone.
Keep in mind that since the pre out voltage of most mobile devices is low and they often start distorting at full volume, I would suggest that you set your gain settings while you are at only 75% or so of the phone's max volume to be safe and get distortion free output.