What is a good workout routine for a 14 yr old boy looking to get lean and muscular in 3 months time?

hi im 14 yrs old and i have been working out for a while but im not achieving what im looking for. first off i need a good routine that will get me lean and muscular, im not looking for getting a ripped six-pack, just lean and somewhat visible. My stomach is kinda fat and i need to get it down. I have decent arms and a pretty good chest I want my arms and pecs to be cut and muscular. i weigh about 134 pounds and really need a routine that will get me the results i want in 3 months. PLEASE RESPOND :) THANKS!