If the master sits level in the car you can do it while it's still on the car, otherwise you'll need to remove it and
carefully clamp it level in a bench vise. You'll need two plastic adapters with the appropriate thread size for the master cylinder and two sections of line to run from the adapters back into the reservoir. Most auto parts stores have a universal kit to do this. If you have any scrap sections of steel brake line handy that have the correct fittings to match the master cylinder that will work as well, just cut them to length and bend the lines in a semi-circle so that when they're attached the line routes back into the master cylinder wells. Make sure the ends of the tubes (or lines) are at least 1/2 way down into the wells so they stay submerged.
Fill the reservoirs with fluid and slowly stroke the piston in & out the full length of its travel. You will see bubbles coming from the submerged ends of the lines as the air inside the master cylinder is purged. When you don't see anymore bubbles the master cylinder is bled.
Alternately you can cap off the discharge ports (using plastic fittings like the ones that come on most new/rebuilt master cylinders) and use the same basic process as described above until you don't see any more bubbles coming from the feed holes in the reservoirs. I prefer the old-fashioned way (with the tubes/lines) myself. Below is a youtube video showing how to do it with the plugs instead.
https://www.youtube.com/watch?v=_VMXC2xsy2s