Hi Nebo,
The reason why you cannot click Next is because you are trying to create a table with a space. The pop-up reads "Field names may only contain alpha-numeric characters.". So once you remove the space, it will allow you to create a new table.
It looks like you already have an Affliate table. Is this the table you want the dropdown to pull from? From the Screen Editor you choose the dropdown values based on exiting table (Step 4).
This should correct the issues you're experiencing. Let me know if that works.
Sam