Hi Barbara,

The answer is the same as for these very similar questions:

Eurail passes cover you for multi-stage rail touring holidays, but individual tickets can be bought directly from the provider just as they can in America. Direct trains between Munich and Paris are run co-operatively by the French and German state railway companies, so you can buy from either, but most people find the German site (bahn.com) easiest to use. You have to book these trains in advance and with regular tickets, the earlier you do so the cheaper it’ll be.

Hope this helps somewhat :-)