S4S version 2.900.18222.3 and above allows the manipulation of the custom S4S xDB contact facet from within Salesforce. There is a lot of functionality included in this package, but the basic function of rules based personalization within Sitecore is the same.
Fig 1: You have added the personalization button to a Lead or Contact. In Salesforce choose Sitecore Personalization from the dropdown list of actions:
Fig 2: Sitecore Personalization options
Next
Congratulations, you have finished installing this option.