All international connections can be booked in advance here : https://www.sncf-connect.com/en-en/

For internal trains, tickets can be booked directly in the train stations, online or through the app. Timeschedule can be checked here  : https://www.sncf.com/en

A well-developed networks of motorways (A50, A55, A7) makes access to Marseille by car fairly easy.