You can add additional suppliers to products in Dropified with the following steps: 

1. You'll want to go to the "Connections" tab of the product in Dropified and click the "Add Supplier" button.

2. Enter in the requested information and click "Save Changes"

3. Once the additional supplier is saved, this usually makes it the default supplier automatically. If you want to make the previous supplier the default one, you'll click the "Make Default" button next to the supplier to make sure that is the supplier that is used when placing an order.

After you add the new supplier, you can map the variants with the Variants Mapping feature.

Learn about Variants Mapping and Advanced Mapping here: http://help.dropified.com/en/articles/2707853-variants-mapping-and-advanced-mapping

You can also watch this video demo that walks you through the process of adding different suppliers to your product: