In order to use the bpost plugin for Woocommerce, you have to configure :
- a valid default sender address in your Shipping Manager
- a price range for each delivery method in your Shipping Manager
- one of several shipping zone(s) in Woocommerce
1- Configure your default sender address in Shipping Manager:

Configuration of your default address (sender address).
 This address is used to return the parcels under status "back to sender". Please indicate a valid one. 

2- Configure your prices (charged to the end-customers) 1/3:

2- Configure your prices (charged to the end-customers) 2/3:

2- Configure your prices (charged to the end-customers) 3/3:

3- Configure your Shipping Zone in Woocommerce:
in Woocommerce > Settings

Go to Shipping > Shipping Zones
Click on "Add shipping zone" to match bpost delivery methods to shipping zone of your choice

Name the zone, select the regions/countries, and click on the "+" icon to look for and select "bpost shipping"

Additional information on this link:
https://docs.woocommerce.com/document/setting-up-shipping-zones/
