Train

At the top of the page are two sticky threads. The top one is FAQs. The second one is titled " How much time to get there? & itinerary questions answered here". Click on that and then train times, the first choice below. That takes you to the Bahn, Germany's railway company with information about all of Europe. Put in the stating point and end point of each segment, the day you are interested in (the same day of the week next week is quick and easy and pretty close to later in the year) and the time of day. If you have difficulty interpreting the results (try clicking on the little grey triangle) come back. They will have answers to all the questions in your OP. Happy planning....

When you say you do not understand how trains work, I am not sure what you are asking. They work just like the airplanes, buses, and trains in the US. Some trains go direct from one major city to another often with a few stops in between. Often though, you need to change trains one or two times just like flying from Bellingham to New York. Train travel is much easier than US air because you don't have security issues, long check in lines and changing trains is matter of walk a few yards. Service is so frequent that you can go about anytime. So, tell me exactly what you don't understand, and will try to be more responsive.
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German Rail has over 41,000 km of track and 5400 stations. There is almost nowhere in Germany that is not accessible by rail, and there are bus systems for the rest. French Rail and German Rail run high speed express trains between Paris and Munich via Strasbourg in about 6 hours. For Munich to Zürich, you have several options, via the east end of Bodensee, Lindau to St. Gallen, via Friedrichshafen and across the lake by boat, via Singen on the west end of the lake, and via Stuttgart and up the Rhein via Basel. Find schedules and some fares on the German Rail (Bahn) website. You can use the Anglicized spelling of München, Munich. For Zürich, Zurich will get you the airport. Use Zuerich for the town itself.

You won't need to worry about train service in Europe. They are everywhere and they mostly go right into the center of cities, towns and villages. Multiple trains depart Paris each day for Munich. You might have to change trains along the way but that's the way the systems work in Europe. Distances between cities in Europe can be 6-8 hours by train and often require train changes. In the U.S., most people haven't been near a real train station for most of their lives. Airports yes. Train stations, no. In Europe, it's a very common method of travel. Major train stations in Europe have hundreds of thousands of passengers going through each day. After you purchase a few tickets and make a few runs, you will get quite used to the trains. If you can be more specific with your itinerary and travel dates, people on this site can provide you with actual information on the train runs you would need.