There are two ways you can model a sloped line:

Method 1: Expand the "delta field" area by clicking on the "chevron". On the right side of the expanded dialog is a length field with direction cosines below. Define the first element properly using DX, DY, and DZ. For subsequent elements you only need to specify the length. CAESAR II will assume the same direction cosines and correctly populate the delta fields.

Method 2: Code the line horizontally. When you're finished, use the "block rotate" to drop the line down "x degrees". Make sure you use the [Setup] option on the "rotate" dialog to disable the rotation of restraints and displacements though.