Yeah, outside the gate there are three trees that have targets painted on them. If you walk into that area from another one, you should see a Lightfoot whacking three trees in a specific order. The gate opens and he walks in. You then hit the trees in a similar manner with your staff, and the gate should open. If for some reason the Lightfoot isn't there (or perhaps you saw him already and didn't know what to do), just whack the three trees until you get it. He should do the tree thing, though, and that's how you get in.