I need a basic primer on interpreting vacuum tube datasheets
As Dave said, you don't have to actually run the tube in a real circuit to get the visual effect.  All you have to do is power up the heaters.

Your particular tube actually is two tubes in one package and has two heaters.  Each heater is 6.3 V.  You can put 12.6 V accross pins 4 and 5, or 6.3 V accross both pins 9-4 and 9-5.  In the latter case, you connect one side of the 6.3 V supply to pin 9, and both pins 4 and 5 to the other side.

Don't worry about the exact voltage that much.  These things were intended to be run directly from a 6.3 V output winding of a power transformer.  It will be OK with variations of this 6.3 V due to input line voltage variations.  Get a "6.3 V" transformer intended to run from whatever power you have in your location and the tube will be fine.

You do have to make sure the transformer is rated for the total current of all the heaters together.  For example, if you are powering 5 heaters that all take 6.3 V at 300 mA, then the tranformer output must be rated for at least 1.5 A.