Custom Fields connected to DB

I’m trying to create a custom field that connects to an api / sql query. I have everything set up on the sql query I just can’t remember how to add it to custom fields in infusionsoft. Right now I’m in Admin > Settings, when trying to add the field I remember I had to prepend an underscore to the field name to reference the sql query but where do I enter that? I see where I can click “View the field database names (for the API)” but none of the database names have an underscore (and I have other custom fields) so I feel I am in the wrong place. Please help!

You should add an underscore only using custom fields names in you API queries.
Creating a field in the Infusionsoft UI, there’s no need to manually add this underscore, you just enter the plain title (the actual database/API name is generated by Infusionsoft).
The list shown by “View the field database names (for the API)” outputs these generated plain names, without underscores, so that’s normal.
For example, you added a custom field with a title My Field, and have a database name generated/shown MyField0, then you should use _MyField0 in your API queries.