FYI- My instructions will make a lot more sense if you have the Deka curtain rod in front of you. Deka comes with a wire, two post screws, two cylinder thingambobs, two end cappers, and a bunch of clips (I just made all those names up because IKEA doesn't include actual words with their instructions). Decide where you want to hang your gallery. Screw the post screw into the wall. You will need to buy your own screws and wall anchors (IKEA doesn't provide those).
Insert curled end through one of the holes on the side of the cylinder. You will need to determine which hole before you insert the wire. Do this by twisting the cylinder onto the post screw that is attached to the wall. Put a tiny sharpie mark next to the hole that you want the wire to come out of. Don't skip this step! I did at first and had to start over.
Pull the wire out as much as you can. There will be a small loop left inside. That's okay. Now twist the cylinder onto the wall mounted post screw. Watch out for the wire as you are twisting.
Twist the other cylinder on the the other post screw. thread the end of the wire through the holes and attach the end cap (pulling the wire taught). This step is easier if you have an extra set of hands. Trim the wire.
Good luck! Please let me know if you have any additional questions. I will do my best to answer them!