How to make back- loop curtains into pleated drapes ?

Hmmm...Not sure this is doable. Pleats take up double the space of a curtain panel. If you were to pleat them, they would shrink to half the size of your panel. However, you could buy (if they're still available) more curtain panels but then they wouldn't fit when you closed them because you would have double the size of the curtains.

Another idea is to buy the "clip on" curtain rings and clip them on to the headers of the curtains every so many inches which will create pleats. But again this will shrink your curtain panel. You could always add a complimentary colored curtain panel to fill in the space needed after you pleat them.

A great tip for pleating curtains, is to wash them if they're washable, hang them up damp (using the clip on curtain rings) and hand pleat them. Tape paper strips around each pleated panel (like they do at the dry cleaners) and leave them up for about a week. Remove the strips and you have nice pleated panels.

Good luck!

I have back loop drapes and when I open them I just pull the areas between the loops away from the window so they all look uniform

you can buy pleating tape to make pleated curtains

Pleats are very hard to make. As a seamstress, this would not be something I would tackle. I wish I had a good answer for you. Maybe we will both get some ideas.

The easiest way is to take the space between each back tab. Pull it out, wrong sides together as it would be on the rod if you had two tabs pulled together side by side. With the top lined up evenly, pin in place. Stitch down close to the two tabs, about 3 inches. This the pleat. You need to decide what kind of pleat you want, then fold the fabric into that shape and bar tack at the top or the bottom. Bar tack is your zig zag stitch with no stitch length. On some machines you must lower your feed dogs. The width should be the same as the back tab curtains when the are open. However they will not close to cover your window. They are simply side panels. Hope this helps!