Simple enough, use one of the angle guides available on the DLS, point it in the direction you want to go and start placing the track. The guide is only 5 km long so you will need to l=place several end to end to cover the full distance. Track doesn't attach to these guides so you just have to eye-ball it. There are other track guides that do allow track to attach. Use two with track between them. Then move one to the end point and the track will stretch between the guides. If you attached two tracks, they will be nicely parallel.