WordBuilder is a VST MIDI plugin and SONAR MIDI plugin, not a VST instrument. The major sequencers that support this type of plugin are SONAR 4&5, and Cubase SX 2&3. If you will be using WordBuilder in either of these sequencers, load WordBuilder as a MIDI effect (SONAR) or MIDI insert (Cubase SX) on the track that will send MIDI to Symphonic Choirs.
If you are using another sequencer which doesn't support MIDI plugins, you will have to use the WordBuilder standalone.