Were these directions packed with the new filter?

They are printed on the original filter. And they are the same all over the internet for that filter number. I haven't gotten a new filter yet, I was figuring out how to install it first.

The NL 300 replacement is a 4396508.
If your old filter unit easily pulled straight out, it may not have been secured all the way in when it was installed. Then a calcium buildup might have obstructed the new one seating completely.
You might try spraying vinegar into the filter chamber and reinserting the old filter overnight while things loosen up. Then try to get the old filter to lock properly and once you can do that, spray rinse the chamber and install you new filter.

Here is a link that might be useful: youtube demo

Thank you for the video, laat2. It confirmed that I was trying to install it correctly. I figured out that the cap that slides onto the end of the filter as a handle is the problem. It won't go all the way into the hole so it prevents the filter from seating. I seated the filter by itself temporarily. I assume that will be ok until I have more time to see why the handle doesn't fit.
I appreciate your help.