Prepare eyes

• Turn on deformations by pressing O.
• Select Enable Deformers so they are visible to the camera
• Put each eye into separate Item mesh layers
• Select each eye Item individually and center pivot points inside each eye > Edit > Center to Bounding Box > Center

Setup Tab

• Select the Setup tab up the top and then press the Setup button (the viewport will be highlighted) - this effectively turns off deformations temporarily. Leave it on until the end.
• Select one eye at a time, under the Commands menu > Deformers > Transform  . This will add a transformer inside the eye item. It will also create a Transform Effector, which essentially is a locator that the eye will become constrained to.
• Rename the Transform Effectors Left & Right. As they will both be created in world space sitting at 0,0 they'll be difficult to tell apart.
• Making sure that the eyes are visible (i.e. hide any distracting layers), from the Item List

• Select one Transform Effector at a time, and while Match Position is selected, click on Drop Action and then drag'n'drop into each eye.
• You can reduce the size of these Effector locators under  > Display > 3D Items > Size 
• Select both locators and duplicate them, and then move them to out in front of the face.
• Duplicate one of those locators and move it hoizontally so that it's in between the two.
• Parent the locators to the central one which is now effectively the main controller

• Now we need to create a directional constraint by selecting the left eye transform locator, and then shift-clicking on the left locator out the front.
• Under the Modifiers tab, select Direction. Repeat with the right eye.
• To test that it works, turn off Setup mode.