At first, there was some head-scratching. The ML-L3 didn't come with an instruction manual. The instructions are in the Nikon D7000 Manual on page 80! I'll summarise it here (for Nikon D7000):
1) Press "MENU" button on camera body. Select the icon that looks like a camera (ie. "SHOOTING MENU").
2) Scroll up or down until you find "Remote Control Mode", then press "OK". The default is "2s(seconds) Delayed Remote". I chose "Quick-response remote" meaning if you use the ML-L3, the shutter will fire immediately. There is also a "Remote mirror-up" option for Mr. Fancy Photographer. Once you've decided which option you want, press "OK". I suggest you just select the "Quick-response remote" option and press "OK" coz you want to see immediate results, whether your ML-L3 works or not. Later on you can get fancy. Now, exit from the "MENU".
3) Now go to the "Release-Mode Dial", that knobby dual-dial thing on the top of the camera body that has the letters "S, CL, CH, Q, Timer icon, ML-L3 Remote icon and Mup" options. You have to press the "Release-Mode Dial lock release(!) black button just next to it to turn the "Release-Mode Dial" to the "ML-L3 Remote icon". Phew! So far so good! Stay with me now, buddy! :) Have a sip of water...
4) The Nikon D7000 has 2, yes TWO infra-red receivers! The FRONT receiver is just above the "D7000 logo" , and the REAR receiver is to the right of the "OK" button-wheel-thingamajig. What does this mean? You can be behind or infront of the camera when you use your ML-L3!
5) The ML-L3 is fantastic. I absolutely love it. Regards from Malaysia :)