you will need a weighted pressure cooker and a good size length of tubing, coiled tubing is best if you can get hold of it.
1) Remove the weight from the pressure cooker so the hole is exposed.
2) place 2 other pots by the cooker, one empty and one filled with clean water. for topping up.
3) fill the pressure cooker and second pot with unheated water and coil a lot of tube length in it to allow the steam to empty into the third empty pot
4 ) turn cooker on to a slow boil steam will pass throgh to the second empty pot which will be the distilled water
5) top up with the pot of unheated water so you do not have to leave the cooker
6 ) turn off the cooker before it is boiled away