Where are you going? It can vary from spectacularly easy to very demanding depending on the type of train and how busy it is.
Spent years going up and down on Eurostar with mtbs and road bikes – just rode to the station and put the wheels and frame in a couple of large bin bags. This doesn’t seem to work anymore. Got intercepted on two occasions and directed to Eurodispatch where you pay £25 each way.
It’s much easier on the TGVs in France – never had a problem although it’ll depend entirely on the staff on the day. If you’re on a double decker, there’s usually plenty of space. Sniff around for alternative luggage racks as the obvious ones are always full.
