It's much more gentle than it sounds. You can climb with your hands anywhere on the bars, but for most people the most efficient place to climb is with your hands on the top of the bars - if you have relatively wide bars you can even move your hands in from the hoods and hold the bars on the tops. Try to grasp them gently - don't put a strangle hold on your handlebars and try to yank them up and down. As you are climbing gently (again with the gently) rock the bike back and forth and you will find that you are naturally pulling up with your arms as you push down with your legs. But like I said the key is to do it gently and fluidly. If you thrash about you'll just waste energy and you won't endear yourself to anyone who has to ride near you. Just think about Phil Ligett when he talks about a rider "dancing on the pedals" - you want to try to be graceful.