Read data from external database - How to create a DB Connection

Hello,
i am new to ChronoForms which looks very mighty. Now i want to read data from a table from an external database. I use the action read database and the advanced setting external database. But there I have to select a DB connection - where can I create these?

That's under the form "settings" area, where you set the form name, under "Advanced"

Thanks, now it works pretty!