There are actually a few options for doing this; it depends on how much work you are prepared to do!
The easiest way is to use this service:
http://www.image3d.com/stereo/index.html
If you send them your image pairs, they will produce a View-Master reel for you. All you need to do is take the pictures (and pay them!).
The hard way is to use a kit like this one:
http://www.3dstereo.com/viewmaster/vm-mar.html
For this you will need to format your images according to the instructions (using Photoshop) and then you will need to find a lab that can transfer the digital photos onto 35mm slide film. I live in the UK, and there is a company here that can do this:
http://www.digitalslides.co.uk/detailed ... l-cameras/
I'm sure there are similar labs around the world.
You will need to make sure that the dimensions and proportions of your images are exactly right, so that when they are converted into 35mm slides they will be the correct size and shape to be inserted into the blank View-Master reels.
Once you have the slides, you will need to cut out the individual images (carefully) and mount them in the reel templates. In the old days, View-Master produced dedicated film-cutters to work with their own cameras:
You can still find these second-hand on Ebay, but they are of limited use when using slides taken from a different kind of camera; the images won't line up with the cutters, sadly.
There is also another option, if you want to produce your own stereoscopic slides: you can mount them in the Realist Format, which was by far the most popular consumer 3D format of the mid-Twentieth Century.
The mounts for this format can be purchased here:
http://www.3dstereo.com/viewmaster/rbt-wid.html
or on Ebay:
http://www.ebay.co.uk/itm/370434727045? ... 812wt_1396
With this format, the images are much easier to process; you just send the left and right images to any lab that can convert them to 35mm slides and have them printed full size. Make sure you instruct them
not to cut or mount the images. They will send you a roll of slide film, and you simply cut out the images and mount them in the blank Realist frames.
The slides can be viewed using a modern viewer:
or a vintage viewer:
The image quality is stunning; 35mm slides are much higher resolution than any video or computer format (some estimates put the resolution at approx 24 megapixels) and this is by far the best way to view stereo photos. The FOV of a Realist viewer is also very large; much greater than any consumer level head-mounted display.
I generally mount my best photos in this way. It's a great way to see them!
Good luck!