Place the rose petals either in the bottom of the still with the water or pour them over some sort of grill that will allow the vapor to pass through the petals, but that will keep them above the water level. (Some stills have an extra section made for distilling plant material in that way.)
Make sure any seams between the various components of the still are sealed in some way so that the water vapor doesn't escape. (Some people use clays, others use plumbers' tapes.)
Find a way to cool the coiled tubing of the still. Normally this section is in some sort of container that can be filled with ice water. You can also run a continuous flow of cool water over the tubing once you see water vapor forming. (Save the water used for watering plants!)
Heat the water in the bottom section using either a gas or electric stove. (Or use whatever else you may have on hand. Some stills are electric and just need to be turned on.)
As the water boils, the vapor will move up through the rose petals to the tubing at the top of the still. At the top, the vapor normally exits and makes a turn to the side. It then moves down to the coiled tubing.
As soon as you see signs of water vapor forming, add ice or cool water around the tubing to help condense the rose hydrosol.
As the water condenses, collect it in a clean storage jar.
Keep running the still until most of the water has evaporated from the bottom of the still or until you have enough rose water.
Using the stovetop
Place water in the bottom of a large pot.
Add the rose petals either directly in the water or over some sort of strainer that will allow water vapor to rise up through the petals without them actually touching the water below. (You can use a pasta or steamer insert for this.)
Make room in the center of the rose petals for a medium-sized clean, heat-safe bowl and place it there. (If you are adding the petals directly to the water, place the bowl over something that will keep it from touching the bottom of the pan. This helps prevent evaporating our finished rose water.)
Add an upside-down lid to the top of the pot. (Avoid using glass to prevent stress fractures of the glass due to extreme temperature differences.)
Heat the pot to boiling.
Fill the inverted lid with ice.
As the water boils, the water vapor should go up to the lid and condense there due to the coldness from the ice. It should then drip down into the bowl in the center of the pan below.
Occasionally remove the condensed rose water to prevent it from evaporating away and to make room for more. Continue until most of the water below has evaporated, or until you have made enough. (Leave some to keep the petals from burning as that will affect the fragrance of your finished water.)
Notes
A more fragrant rose water can be made with fresh rose petals, but you can also use dried petals if it's all you have.Sanitize the bottles with alcohol before storing your homemade hydrosol in them. This can be done by swishing a small amount of high strength alcohol inside the bottle, pouring it out, and allowing it to dry before using it. Store the finished rose water in a cool, dry place for up to several months- or use a preservative and store in the fridge to keep it lasting longer (up to 2 years). You can use a combination of .15% potassium sorbate + .05% citric acid to help preserve the hydrosol during storage.Other ways to extend the shelf life include using more opaque bottles (although that has the disadvantage of hiding unusual changes in the appearance). Keep the bottles with as little airspace as possible by filling them as far as you can. Avoid contaminating the hydrosol by not dipping into it. Keep the bottles tightly sealed when not in use.