From the Lost Boys car park, follow a well worn trail West to the crag on rolling terrain. You'll see a short quartzite cliff to your left after about 15 min; follow this for another 5 minutes until you arrive at the main climbing area.
Check http://www.summitpost.org/mountain/rock/365957/lost-boys.html for climbing routes.
Directions:
South of Jasper about 20 min on HWY 93A. Pass the park gates south of Jasper and turn off on HWY 93A. Follow this about 25km past the turnoff to Marmot Basin and Edith Cavell. Past the "Meeting of the Waters" where the Whirlpool river joins the Athabasca, look for a small pull out on the right just large enough to park 2 cars. If you make it to Leech Lake parking, you've gone about 200 m too far. You can also park there and walk if parking is full at Lost Boys.