To bring up the plugin right-click on the request you want to test and select 'Send to' -> SQLmap:
The plugin provides an easy to use interface:
There are predefined menus for typical sqlmap options like Technique, Risk and Level. You also can add any command line option manually, e.g. for further enumeration tasks.
When you press the start button WATOBO will first write the request to a file in the temp directory which will be parsed by sqlmap (-r option). Then it opens a new command window and runs sqlmap.