Use the elbow at the sewer connection and the straight end at the RV. I also would suggest a straight or elbow clear at the RV end to allow you to visually see what is being discharged...when draining your black tank (keep closed till full or almost full) you can see when it runs clear when flushing the tank. You also may want to get a slinky, to support your drain hose for proper drainage.
The rv end will have three or four tongues that will lock onto the lugs on the RV after you remove your cap.
2011 Toyota Tundra double cab