Assuming you're going to be using a mono boom mic, I used to plug mine directly into one of the RCA jacks. I never had an XL1, but an XL1s. If the setup is the same on both you'll need an XLR-to-RCA adapter, some cable and a male RCA plug to go into the XL1. Depending on how hot your mic is you might need an adjustable XLR attenuator to drop the signal down a bit. Using the MIC ATT setting in the XL1 is also an option but it might drop the signal too much depending on the boom mic's sensitivity.
I'm in New Zealand and have an XL1s. I'm not sure if they have the same fittings as yours. We found an adapter at an electronics store that we could plug the 3 pin microphone cable into which went straight in to the microphone socket on the camera. Later we plugged the microphone in to a small mixing desk and then into the camera. Hope this helps.