Every document library has sources: the rule for which recordings feed it. The desktop app builds that rule as an inline query; the dashboard builds it from saved filters.
Sources in the desktop app
The create library screen has a Sources card. Either turn on the Include all recordings switch, or leave it off and build a query; you must do one or the other before you can create the library.
The query builder works in groups: Add filter adds a condition to a group and Add filter group starts a new one. Conditions inside a group are joined with And, and groups are joined with Or. The fields are Status, Application, Step type, Text and Recorded, with options drawn from this device's own recordings. The desktop app covers one device, so there is no device choice.
After creation, the library's Settings tab shows the same card with the switch labelled Process all recordings.
Sources in the dashboard
A dashboard library's sources are one or more saved filters, chosen when you create the library and changeable later in its settings. At least one is required, so if you have none yet, save a filter from the Workflow map first.
How sources feed a library
Sources are checked as recordings arrive: a new recording that matches a library's sources feeds that library. What happens next depends on the library's writing mode. Automatic writes documents from every matching recording, Review holds them for your approval first and Off pauses writing.