Mostly it's analysis and common sense. We don't know how your drapes are constructed, so we can't give you a step-by-step on how to deconstruct and hem. Take a look at the sides and bottoms. They may have to be picked apart with a seam ripper; maybe they can be measured and cut. At any rate, they will have to be measured up, pressed and cut. They will have to be turned and re-hemmed. They should look exactly as they do now, only shorter (maybe better). Some of your work could be from the inside out, turned and seamed and then hemmed. It's hard to tell you, but the best thing for you to know as a new sewer is that you can look at a project, analyze it and reconstruct it to your specifications! You can do it!

Thanks annie
Mostly that I need encouragement like yours - I sort of get analysis paralysis when starting a new project

If I get stuck I'll post pics
thanks

If you have a pair, take appart just one panel, measure,cut and put it together using the other new panel as a sample. I don't know how Penneys drapes are made, usually the lining is not attached so it is easy to shorten them.
Need to open seams on both sides about 15" or so and open the bottom hem on drapes and lining.
Press the old hems out flat, measure and cut off the amount you need.
Make double hem or duplicate the hem as it was and sew.
Finish the sides as before. Don't forget put in back any weights-if they were in.
If the lining is attached, let me know.
Hem on the lining-use straight stitch, there is no need for blind stitch, drapery hem, use blind stitch if you can or hand stitch it.The sides should be done this way as well.
As Annie said, don't be affraid, just be carefull w/the seam ripper.If the hems are sewn using a blind stitch, it is easy to take it out.It is just like a chain stitch, one long thread, just find the right end.