Hi! Having problems with my humidifier model 758.144071. It runs continuously and I am not sure if I am placing the filter(s) in correctly.

This is a very simple product. It's basically a bucket of water, a fan, and a humidistat. The humidistat is responsible for cycling the unit to maintain the moisture level you are asking for. During these colder months, your furnace is going to naturally burn up most of the moisture in the air in your home, so I would certainly expect it to run more than it does in other times of the year. As long as the fan is running, the coils (if visible) are clear of dust, and the water bucket is becoming empty on a regular basis, then I think I would wait to see how it functions in the warmer months of the early spring before suspecting a failure. One way to check for excessive run is if you have water condensing on your windows on cold mornings. If you don't it's probably fine. If you do, you can try to reduce the humidistat setting to see if that helps. As for how you are installing filters, you would probably just check the owner's manual, since that is usually a visual kind of thing. Good luck.