According to MSG.com, to view the game in 3D at home you will need a 3D television (who the heck has a 3D television?). Next, the three Ranger fans that do have this 3D television can tune in to iO TV Channel 1300.
As far as where to get the glasses, I have no idea. I don't see anywhere on MSG.com that says where to get them. I'm assuming you can pick them up at any Cablevision store in the area.
Or you can save yourself a lot of trouble and just go to the 3D viewing party at The Theatre at Madison Square Garden.
...while the idea seems pretty cool, unless you're going to the viewing party or have a 3D television you can't watch it in 3D. So basically MSG and the Rangers are doing this for about 500 people. Sounds like a waste of money. Which the Rangers have grown accustomed to doing (See Redden, Rozsival and Drury's contracts).