Measure the height of your window and compare this to the length of your curtains. Lace curtains should hang at least 3 inches above the floor to avoid being torn by vacuum cleaners or stepped on by people or pets. Determine how far above the top of the window your curtains need to hang and mark this spot.
Install your curtain rod, according to the manufacturer's directions, at the appropriate height, about 1 inch from each side of the window.
Thread the lace curtains onto the larger part of the curtain rod--the part that goes on the outside when you put the two halves together--very carefully to avoid snagging or tearing. Putting them on the larger part first means that you won't have to pull them against the ridge that is created when the rod is assembled, and can avoid catching the lace.
Hang the rod with the curtains on it, and straighten them. If you are hanging solid curtains or draperies over the lace curtains, be sure to use another rod, slightly above and to the outsides of the lace curtains.