There are a variety of ways to get 3D images into a 2D medium, and each one has its own advantages and disadvantages. But so long as the result is that the left image is seen by your left eye and the right image is seen by your right eye, you'll get the 3D effect.
Some methods require additional glasses or viewers. These methods are the easiest to view (so long as you have the required tools).
Colored Glasses: The most common of these is the colored-lens glasses -- glasses with one lens red and the other cyan (or other color combinations, but rec/cyan is the most common). Most of my images are presented for this viewing method, since it is so common and easy to view. I include a pair of glasses with print orders, but you can also order them cheaply online from Amazon and others).
Stereogram Viewers: A bulkier handheld viewer is the stereogram viewer and its kin, like Viewmaster and Google Cardboard, which use optical lenses to redirect and refocus your eyes to two separate images presented side-by-side, with the left image on the left and the right image on the right. These are superior to the colored glasses method in that you get full color to each eye. The drawback comes in cost and bulkiness.
Cross-eyed Freeview: The apparatus-less viewing method requires only practice to train your vision to focus in a novel way. In this method, the two images are presented side-by-side, but in the wrong order: left image on the right side and right image on the left side. To view these images properly, you cross your eyes (so that you're looking at a space in front of the image pair) to get your eyes looking at their respective images. The practice then comes in refocusing your eyes to the depth of the monitor (or printed image) while maintaining that crossing. This can be difficult as your brain has had years of experience that tells it to focus at the point at which the eyes are looking. But stick with it. Five or ten minutes the first time becomes a few seconds the tenth time, and it eventually becomes instinctive. The result is full-color 3D any time, with no glasses or other contraption to fumble with (or forget).