Army question?

i just got my ged i want to get into the army then go to ranger school but some people are tellin me i cant ,... some tell me i can some say i have to be e-4 ,.. my case it would probly benifit me .,, i also hear that it is near impossible to get it in your contract these days,..what will happen if i dont get in after i enlist and done with my bct and airborne training, i no its better to apply first than to do it later,,