In order to add new fields to your Data Source, you must go to the Data Source configuration screen > parse screen (which updates the schema in Openprise based on the Salesforce configuration with the new fields) and then to the map screen. On the map screen, make sure to check the box for the new attributes to have them included in your data source. The next import will import the newly added fields for those records pulled in during the import. Note that to have the new attribute pulled in for all records in the data source during the next import, you will have to first purge the data source and then re-import all records.
In some cases, data isn't imported from Salesforce because user credentials associated with the import data source do not have permission to access the missing data. In this case, contact your Salesforce administrator to obtain the correct access.