Hello Nikhil,
After you have configured EasyPost, you will need to configure Business Central. Please see this knowledge base article on how to do so:
https://kb.dmsiworks.com/knowledge-base/getting-started-with-dynamic-ship/
Once you have configured Business Central, you can generate a label by following the steps in this knowledge base article:
https://kb.dmsiworks.com/knowledge-base/how-to-complete-a-basic-shipment-with-dynamic-ship/
You would not need to enter a value for the shipment as that is sent directly from UPS via EasyPost to Dynamic Ship.
Please let me know if you have any more questions.