This option allows Marketo to add and remove members from MS Dynamics Campaign.
Update to the latest version of the Dynamics plug-in for Marketo.
Admin Permissions Required
In your My Marketo, click Admin.
Click Microsoft Dynamics.
Under Sync Options, click Edit.
Select the Enable Microsoft Dynamics Campaign Sync checkbox and click Save.
There you have it. Just give the sync some time to pull the data from Microsoft Dynamics and you are good to go.
Resetting the Dynamics Campaign Sync checkbox will refresh all the previously synced Campaign data and the associations with the Marketing Lists in Dynamics.