From the Sitecore core database - create a Template called SalesforceAccountLookup under:
/sitecore/templates/System/Security/SalesforceAccountLookup
On the Builder tab of the new template, create Data section fields for each profile property that will be mapped.
Using the new template created above, create a record under:
/sitecore/system/Settings/Security/Profiles/SalesforceAccountLookup
Note the itemid GUID of this new item for the next step as it will be used for the defaultProfileItemID in the configuration of the domain.