Step 1. Go to store
Step 2. Buy rose water
Step 3. Enjoy, in fact, buy several, and in addition to adding to your soap, make some Turkish delight, or some baklava.
Seriously. I know you want to gain something from what grows in your garden, free of charge. But what you want to do, for the possible yield, is not very worthwhile. If you want to setup a home brew steam distillation rig, to make your own rose water, you may be able to find info and supplies on the web.
But the traditional extraction solvent for attar of roses from rose petals is benzene. I know. I looked it up as a teenager, and even bought it at the hardware store. And I tried it. In my parent's home. And that was very stupid of me. Benzene is very hazardous, they don't even sell it at the hardware store, anymore.