Two versions: if you have flexible eyes go for the larger set, if not, start with the smaller set to adjust to this technique.
Sit back a bit further than arms length from the monitor to view. Focus on the middle point between the two images and allow your eyes to completely relax as if you were looking beyond the image plane into infinity. Allow the images to meld into one.
View only briefly so you don't develop a lingering headache. For those with bad eyes or tendency to eye strain - just refrain altogether please.
Manipulated 3D image taken of the cooling tower of the now decommissioned/destroyed Trojan nuclear power plant in Oregon.