SMT Resistor array package type
The libraries in the official distribution are not very extensive.  The gEDA way is to find/create your own, you'll likely have your own personal preferences about pad lengths, symbol sizes, silkscreen formatting etc.  There are no resistor arrays in the default libraries to my knowledge.

1206 is a common large SMT resistor package, as you guessed.  It refers to a 120 mil by 60 mil rectangular package.  Some newcomers to SMT prefer to use individual 1206 components, but most use 0805 (80 by 50 mils...you get the idea) for general resistors that have to be hand soldered.  I like 0603, personally, but I like to solder under a binocular microscope.

However, in automatic soldering, it's also a popular outline for arrays: the 4 resistors fit in a space 120 mils by 60 mils.  You'll also find them in 0805 and 0603, but you'll want to stick with 1206 if you're new at this.  After peering into my crystal ball, I'm guessing that you might be looking at a page on RS like this and datasheets with packages like this:  



...and footprints like this:



You need to draw the second image as a footprint in PCB, using the dimensions in the table.

Some parting thoughts: 


Ideally, you'd use a stencil and reflow these components.  However, 4 resistors in 1206 isn't too bad with an iron: It's only a 50 mil pitch, it gets dicier once you start looking at 0.5mm pitches.
Especially for reflow, you'll probably want the concave configuration to wick the solder away from the other pins and minimize bridging.   For SMT arrays, concave means that the solderable surface is inside, on the round part of the castellations, while convex means that the castellations cut through the conductive flat edge of the component.   This may make it more difficult to heat up if you're going to be using an iron, but it takes up less space, because the pads are partially under the component.  
They're quite cheap, get some test parts to see what's easier to solder and double-check your footprints by printing out on regular paper.
If you're worried about solder feasibility, here's a story that should bring you hope: My most-difficult rework job was soldering 36-gauge wires from pin 1 to pin 5, pin 2 to pin 6, and pin 3 to pin 4 of the footprint of an 0603 3-circuit ferrite bead.  1206 outline 4-circuit packages should be fairly easy in comparison...