To create activity records in dynamics CRM 2011 with Data Sync requires a little bit of data formatting to link the appropriate entity and user.
We have a special format that is used to identify the linked entity which consists of an entity name followed by | then the guid of the item in CRM.
A lead entity might look like this
Then its a simple matter of formatting your source data appropriately i.e. below is an example of data you might supply to the phonecall entity to create phonecall activity records.
The Schema map might look like this.
You will notice that the to and from fields are data type
System.String  this is because these can contain multiple values. If you need to supply multiple values just separate them with a semi-colon (;).