It's possible that your model was not made with supports for a ladder. Aljo. and trout are on it. You may be able to add the blocking or if there Jayco may be able to tell you where. Either way start with Jayco if you want a built-in. TxTwo suggests a tele ladder, that'd be my choice.
Our 5th has a ladder and I've used it a couple of times but when home is close by I use my folding ladder. I find the built-in difficult to climb and only use it on the road when I HAVE to go up top.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks