How can I use my Oyster Card on Chiltern Railways trains?

Oyster Cards can be used in 2 ways:

A Travelcard season ticket can be purchased that is valid for one or more of the London fare zones. You can use your Oyster Travelcard on our services between Amersham and London Marylebone and between West Ruislip and London Marylebone inclusive (and all intermediate stations) provided it is valid for the zones you wish to travel in/between. Please note, Oyster Card season tickets must be purchased from Transport for London.

Oyster Cards can also be used on a pay-as-you-go basis. On Chiltern Railways pay-as-you-go can be used between Amersham and London Marylebone and between West Ruislip and London Marylebone inclusive (and all intermediate stations).
Oyster Pay As You Go can NOT be used to pay for any other journeys on Chiltern Railways.