On the sides, fold over the edge ¾” and iron. Then fold it over ¾” again, iron, and re-pin.
Sew down the length about 1/8” to ¼” from the inside fold. Repeat for the other side.
If you want a double folded hem, which will add a little more weight to the bottom, fold the fabric over 4” twice instead. Just account for this when cutting the length of the fabric.
For the bottom hem, fold the fabric in 1” and iron. Then fold it over again another 4” and iron.
If you want to make sure the bottom of the curtain falls exactly where you want, leave the bottom hem to the last step and hang the panel first. Then you’ll know exactly how much to hem.
Starting at the bottom corner, sew up the side, pivot at the top of the fold, and sew across to the next corner. Pivot again and sew along the side to the bottom corner.