I will go with the idea that you are talking about taking a cutting to
root, since you didn't specify.
You will need to find a this year cane that has or had a flower at the terminal end.
Cut this down far
enough that you can strip off three to four leaves at the bottom end and still have two to three left.
Wet the
de leaved end with willow
water or wet it and coat lightly with rooting hormone.
Plant in ground or in a largish pot, water in and cover with a cloche (like a glass 1 gallon pickle jar) and set in partial shade.
This is best done just after the first bloom of the season.
It will take about a month, you will notice new leaves growing once the new
roots are formed.
I've done lots of roses this way and as long as you are careful, you will be able to have a nice new rose.
The actual preferred method of creating new bushes is by bud grafting to a rose root stock plant.
Redhawk