Mongoose Exile 26 Men's Full-Suspension Mountain Bike "derailleur dxr" Questions

dxr 21 speed 26 in. i want to make sure the gears shifter and the chain are right to shift right. When I shift it clicks and doesnt seem to go in correct gear. http://www.parktool.com/blog/repair-help

...dxr 26 inch mountain bike, problem is the chain had been changed and not put back on right is there a diagram that i can see to make sure it is put on right? ...