Example maps:
Some example maps are included in UDKGame\ContentSDK\ExampleMaps, demonstrating some custom Chivalry actors and kismet nodes. Please look these over before diving into creating a map, as they will help to answer questions you may have along the way.
It is very important that you keep the player scale in mind when designing a level.
Hold the '\' Key for a scale reference character when in the view port. He is the same scale as a Chivalry Character.
For Checking Collision on your maps, a handy mode is available in the quick flags menu. Zero Extent and Rigid body collision modes will help you visualize the map collision better than the default view.
As a General Note. Use Landscape, not Terrain. Terrain is outdated.
https://udn.epicgames.com/Three/Landscape.html
Getting started with map editing.