The quest starts at Rodney at level 200+ It's not that hard to figure out. You'll have to find another ranger and assist him. It's worth noting that you cannot leave the room when you're killing the Giant Kodiak or you will automatically fail the quest, so make sure you've got decent HPs & are spamming cure wounds on yourself. Bring the schematic back to Rodney when you're done & he'll give you access to the backroom.
Command: plant
Syntax: plant <trap> [...]
GP Cost: 100
Learn Level: 200, 25 in covert
This skill allows Rangers to hide their traps in discreet locations. Like an
experienced trapper, one can accurately target certain races or players by
predicting their footsteps. Your hiding skill determines how well you can hide
your traps from view.