The Canyon is the third world in the Career mode. In order to reach the Canyon, you must complete the Highlands and Forest worlds by reaching the boss track and crossing the finish line.
This can be done easily and only takes about ten or so minutes following some simple tips.
1) Take it slow, and remember you don't have to follow the path of the track or go off any stunts to complete any level.
2) Complete the easy bonus objectives (such as "Get _ seconds of air time" or "Reach _ kmph") and avoid attempting difficult bonus objectives. This will award you extra lives.
3) Take a direct path to the boss track and choose easy difficulty tracks.
4) For the Highlands and Forest boss jumps, you don't actually have to go off the jumps and land them to travel to the next world. Simply ride around the obstacles and cross the finish line.