The male JST RCY power connector on the cable assembly that comes with the gimbal isn't compatible with the 0.1"-pitch male right-angle header on the ELEV-8 Power Distribution Board. There are a few different options to make the connection. If you have a pin crimping tool, option one should be easiest for you. If you don't have that specialty tool but do have soldering equipment, we recommend option 2. Only if you don't have the means for options 1 or 2 should you use option 3.
For this method, you need one JR-type female "servo" connector housing and pins (such as Pololu #1924; JR Connector 3-Pack, Female [1]) and a specialty tool for crimping the pin connectors (such as the IWISS SN-28B [2] or Pololu #1928 [3]). If you have the right equipment, this is the easiest and fastest method, but option 2 will work just as well for those that don't.
For this method, you'll need a soldering iron, solder, a 3-wire servo extension cable (such as any of the cables in Parallax #751-00010 [6]), 1" of some 1/16" or 1/8" diameter heat-shrink tubing, and a heat gun if you have one. By removing the old connector on the gimbal cable assembly and soldering on a cable that already has a 3-pin female servo connector on the end, you can avoid having to crimp your own connector, but still end up with a reliable connection.
If you don't have a pin crimping tool or soldering equipment, your best option is probably to buy some cable adapters. We've not been able to find anyone who makes a female JST RCY to female JR adapter cable (otherwise we would recommend that), so the best we can to is suggest two adapter cables to use in series. We recommend using a female JST RCY to male JR cable (such as Electronic Model Systems #0151 [9]) and a female to female JR cable (Parallax #800-00043 [10]). Note that many retailers incorrectly identify the connector genders, so pay close attention to the product photos. When using adapter cables, we strongly recommend taping around the connections to reduce the likelihood of them coming loose.
Links
[1] https://www.pololu.com/product/1924
[2] http://www.amazon.com/Professional-Compression-Ratcheting-0-1-1-0mm2-Wire-electrode/dp/B00OMM4YUY/
[3] https://www.pololu.com/product/1928/
[4] https://www.youtube.com/watch?v=EJNEG-lqjuA
[5] http://www.jst.com/pdf/JST_CrinpChart%20(English).pdf
[6] https://www.parallax.com/product/751-00010
[7] http://learn.parallax.com/step-2-soldering-motor-bullet-connectors
[8] http://learn.parallax.com/step-7-apply-heat-shrink-tubing-all-connectors
[9] https://www.google.com/shopping/product/9746616272488734333?q=EMO0151
[10] https://www.parallax.com/product/800-00043