Before getting started, in order to open a setlist in the Playback app from ChartBuilder you'll need:
ChartBuilder and Playback installed on the same device.
The setlist saved to the cloud from ChartBuilder.
(If the "Save to Cloud" option is darker-grey, and can't be selected, it means the setlist in its current state, is saved to the cloud).
With Playback and ChartBuilder installed on the same device, the ChartBuilder setlist can be opened in the Playback app, using the "Open in Playback" option at the bottom of the setlist edit menu (three dots at the top-right of a setlist page).
Note: If it's the first time you've opened Playback on that particular device, you may need to click through the welcome screens in Playback before being able to use this feature.