To Specify a Source Vector for a Distant Light

Click Modeling tab > Render panel > Light drop-down > New Distant Light.
Specify light direction FROM <0,0,0> or [Vector]: Specify a point on the screen
Specify light direction TO <1,1,1>: Specify a point on the screen.
If you enter V for the Vector option, the following prompt is displayed:
Specify vector direction <0.0000,-0.0100,1.0000>: Enter a vector
Select options (Name, Intensity Factor, Status, Shadow, Filter color) to change or select Exit.