In Winamp you can press CTRL+P to get into the Preferences window. There you need to search for the plugin in section Plugins|Input. Double click on it to display the Configuration dialogue. Here you can set:
- the default SoundFont to be used and SoundFont/Preset Overrides for each MIDI Program.
- the overall output level
- the output sample rate
- enable the use of multiple CPU cores
- manage VST effects