Ambient Occlusion

Ambient Occlusion is

Enabling Ambient Occlusion

Enabling Ambient Occlusion is as easy as right-clicking the viewport and heading to your render settings. In the dialog box for your render settings, check the box adjacent from the Ambient Occlusion setting which reads "enable". Make sure that the drop-down menu next to the AO setting reads "AO Only" and not "Outline(link) Only" or "AO & Outline" (edit for proof, add pictures).

Note:If there's ugly black speckles frequenting the scene upon enabling AO, that is usually normal. All this means is that you are not looking through your scene camera with at least 32 samples of depth of field rendered in the viewport (you must be in the Clip Editor).

-Comparison picture: No DoF versus DoF at varying sample rates