Find the right route by train
Taking the train to Europe is a nice way to travel but it can be a bit problematic to book tickets in one place for a trip with several train changes. If your planned trip is complex it can be a good idea to get help from a travel agency who specialize in train travel. You can also explore online sites to plan your trip and book tickets.
For example, The Man In Seat 61 can be very helpful. It is run by Mark Smith, a true train nerd who is dedicated to help people navigate in the train travel jungle. Rome2Rio is another useful site for planning and booking train trips. You will find several other sites if you search for "train travel europe".