Here is sample C# code how to assign a record to a team.
//Assign a record to a team private void AssignRecord(Entity TargetEntity, Guid TargetRecordID, Guid OwningTeamID, IOrganizationService orgService) { try { // Create the Request Object and Set the Request Object's Properties AssignRequest assign = new AssignRequest { Assignee = new EntityReference("team", OwningTeamID), Target = new EntityReference(TargetEntity.LogicalName, TargetRecordID) }; // Execute the Request orgService.Execute(assign); } catch (Exception ex) { throw new Exception("An error occured while assinging Team to a record." + ex.Message); } }