Choose an environment map matching the scene and adjust its intensity
Pick an environment map that suits your scene, tune its intensity, and adjust the sun so it lights the scene from the side you want.
For better renders, select an environment map whose content matches the scene (e.g. one with buildings rather than a countryside lake).
Tune the environment map's intensity instead of leaving it at the default 100.
If the sun is not visible, increase its intensity or readjust its direction/rotation so it enters the scene from the desired side.