1. Select Product Type: Variable product
2. Click on the “Attribute” tabs and add the attributes.
3. Ensure “Visible on the product page” and “Used for variations” are checked.
4. Click “Save attributes” button
5. Click on the Variations tab.
6. Select Create variations from all attributes
7. Click each variation to expand then and reveal their options. Add a price for each, etc.
   
8. Press the blue “Save changes” button.
9. Press the blue “Update” button to publish/save Product.

Related Information:

http://chrislema.com/woocommerce-variable-pricing-one-size-doesnt-fit-all/