Measure the curtains to get an idea of where you need to attach the curtain rod supports. Measure from the bottom of the curtain only to the loops at the top where the rod is attached.
Measure and mark the wall using the drape measurements. Place the brackets on the wall and trace lightly around them to calculate bracket placement. Keep in mind the shape of the rod. Brackets for curtain rods that are wider in some places than in others have to be adjusted accordingly so that the curtain hangs straight. Make sure the brackets are spaced evenly on either side of the window.
Before attaching the brackets, insert anchors into the wall for heavy curtain rods or if the brackets are being placed in drywall. Drill into wall studs if you can and place the anchor in the hole before screwing in the brackets. If you're using self-anchoring screws, you don't need anchors.
With the drill, attach the supports to the designated areas using self-anchoring screws or screws that match the anchors in length.