Within the link that was cited above are the instructions - but this is a step process:
When extension status is
ON,
Additional Settings button will appear. Click to see more settings. Weight Based Shipping method works correctly only if You have configured
Locations in the store and set up
Weight Based Shipping settings for each
Location separately.
First you need to configure LOCATIONS - find them Systems > Localization >Locations
Next you need to setup the Weight Based Shipping settings for EACH location that you setup in step one.
Then when you turn your extension on you will see there are additional settings - where you can configure.
I hope this helps you succeed - if not, keep asking.
Lee
Just another happy Abantecart user