The link you provided causes me a little concern, under instructions they simply say "so easy, none are needed" and on another tab they may the claim that no "power" is needed... yet the signal provides a "pulse"
You will need to contact them and get them to provide some information. I suspect that the device has a three conductor cable, power, signal, and ground... They will need to provide information on which wire is which... Also they will need to tell you if the pulse is a positive pulse or a negative pulse. You can spend some effort to determine this information, but they should provide it for their product...
After you get the above, with the low count frequency, you could simply check the status of a digital pin in the loop function and increment a counter, then once per minute do something the with count value. This would be reasonable only because the frequency is so low. For higher frequencies, or if you simply want a more robust design, use a external interrupt to monitor the signal, and another interrupt to trigger a function to process the signal counts on a time interval (ie. once per minute).