No seriously...just keep riding like someone else said...till your legs hurt and then walk...the more you ride the stronger your legs will get. I am guessing you do a lot of riding cuase I started when I was 13 w/ no job and thats all I ever did cause I had no life. Also, start out with Higher sprockets yes...but if you just stay in them all the time and never change you will start wairing them out. So build yourself up, don't just keep riding in the same one...
Speaking from experience when I first got my Cannondale
I went from riding up hills in first, to riding up hills in 8-12...
It will get easier in time