Fitting Instructions
Although the cable will plug into some connectors either way up, they will only work one way. If it doesn't work, simply plug it in the other way up. It shouldn't damage the lightstrip if you plug it the wrong way up, as long as it's not powered on for hours.
As Phillips didn't design these lightstrips with cables in mind, there is nothing for cables or lightstrips to clip and lock onto. LightStrips only don't come loose because they are stuck in place. In some situations you may need to secure the connections in place with insulation tape or heatshrink.