This is easy. The tricky part is that what is measured is the distance to the next surface. Thus, the object (OBJ) distance is
The distance of the first surface (the AST surface) is the thickness of the lens from vertex to vertex
The distance for the second surface is the length to the image surface. You don't need to set this distance because OSLO can calculate it for you.
So, now add these distances into the table describing your optical system.