I often prefer to sharpen our chainsaws in the wood, as it's a pleasant setting for the task. All you need is a block of wood to sit the saw on, something to sit on, and somewhere to keep your tool box handy:
To keep the saw steady I use this little red clamp with spikes on the bottom, and sit the saw on something to raise it up a bit:
To help with sharpening, I use a "combi gauge", which has rollers to hold the file at just the right height to sharpen the cutters. You get different gauges for different chain types. The red plastic thing is a "magnetic file angle plate", which has lines printed on it at 25 degrees on one side and 30 degrees on the other, to help you keep the file at the right angle. Being magnetic, it sticks to the side of the guide bar.
The other part of the combi gauge is a depth gauge guide, which you use after sharpening all the cutters. It sits over the cutter and depth gauge like so:
The depth gauge on the chain protrudes through the guide, with different settings for softwood and hardwood.
Then you just file it flat with the guide, and the job's done!
Obviously there's other things I've not taken photos of, such as de-burring the cutters and maintaining the guide bar, but that's done without any special tools.