Following the instructions in this post here:
I'm at the part where I'm setting up data sources.
The columns in my 'key stats by date' tab do not match the columns in your example. It's missing the 'cost' column. How do I get this added? Because of that, I can't add the calculated fields to the metrics in the next steps.
The directions have you use a Google Sheet file as a data source, so if 'Cost' is missing from the list in Data Studio, that means that it either missing or renamed in the connected Sheet file. Note that the field names from Facebook Ads themselves have changed over time from when the tutorial was created - "cost" now labeled as "Amount spent" so check to see if that is present instead and use that field.