To use this crafting tool, you first select the type of Greensteel item that you want to create. Once you do that, all of the upgrade options will become available to you. In the individual dropdowns, hover each item for more information.
You can use this tool to craft from Tier 1 all the way up to Tier 3 (Dual Affinity), or you may choose the final upgrade that you want first and build your item backwards. You can even start by picking your second tier upgrade first. It doesn't matter! Plan your Greensteel item how you want to.
Also, if there are any other features that you would like to see added to the "Greensteel Crafting" tool, just post in the forum under my thread and I will see what I can do about adding as many features as are relevant.