In the root folder of your docpad project edit the docpad.coffee file (or docpad.js)
docpadConfig:
...
# enabled example for live configuration
plugins:
livereload:
enabled: true
# enabled example for different environments
environments:
development: # change the name here if you have other environments
plugins:
livereload:
enabled: true
staging: # change the name here if you have other environments
plugins:
livereload:
enabled: true
...
more information about the configuration file is here - http://docpad.org/docs/config