How can I change the default shipping location in my dropshipping app?

Iam doing dropshipping through 3rd party app. All inventory is there. My business address doesn’t have inventory. My business address is listed as default location and I cannot change it. So when clients make an order through my website, shipping charges get calculated based on the location of my business address (as if i was shipping the order from there) not the 3rd party app address, from where orders are actually shipped. How do I change that? Thanks

Thanks for response. I don’t mind. I could use some help. Iam listening.