Your best approach is going to be instantiate a version of the your CR as an object within VB6. First you need to make sure that you can reference CR objects in your VB project so you may have to set up a CR reference to the CR dll. Once you've done that, you can then DIM a CR report object.
Once you do that, you need to create an ADO recordset with the data that you want to print on the report. You can then set the CR data source (or record source or some property like that) to your ADO recordset and the CR will do its thing.
I actually found it better to use this approach with VB6 to minimize the data crunching on the CR side. Do all your data manipulation on the VB side and give CR only the finished data it needs to generate the report. Hope this helps.