Many of our API based Shipping Methods require that your products have dimensions and weights set. Before adding weights and dimensions you should first configure the units and ensure they are enabled:
To enable the weight and dimension fields go to WooCommerce > Settings > Catalog:
Enable the weight/dimension fields
As you can see, this settings page also contains the options for weight and dimension units. Set these accordingly.
After doing this, you can edit a product. In WooCommerce 1.6.x the weight/dimension fields can be found on the general tab. In WooCommerce 2.0.x this can now be found on the shipping tab:
Product settings in WooCommerce 2.0.x
Enter all values in decimal form, without special chars e.g. 12 or 12.5. All fields should be set.
