Quick answer: Select your DAW in the routing wizard to establish the connection to it automatically, or choose the routing settings manually to access the virtual instruments.
Accessing your Virtual Instruments with Liquid Notes
Liquid Notes behaves like a MIDI instrument when connecting to a DAW, and thus can access the Virtual Instruments that come with a DAW. When operating Liquid Notes in Stand-alone Mode, only the built-in synthesizer is available.To access the Virtual Instruments, the routing connection to a DAW needs to be established: a wizard in Liquid Notes automatically establishes these connections for the most popular DAWs when opening a MIDI file / project. It asks you to choose from different Sound Output Sources.
This is how the wizard for the Sound Output Source looks like:
If your DAW is not listed therein, please choose Other sequencer and establish the routing manually. Once the routing to the DAW is established, Liquid Notes will access the Virtual Instruments of the DAW and play through them. This also applies to performing live, when you play to a song!
You may also change the Sound Output Source after having opened a file. Follow the steps in this article to do so - http://re-compose.desk.com/customer/portal/articles/1401971-how-can-i-change-the-sound-output-source-after-having-opened-a-project-