The executeSqlStatement uses the data source you specify in the data source name. The format is java:/datasource_name.
Now how to setup that data source depends on the application server you are using.
In JBoss, like you mentioned, you need to configure a *-ds.xml file to contain the data source information. You can edit one that already exists or create a new file as long as the file name ends with -ds.xml.
Don't change the data source that are alreay setup. Just add new ones.
At this point this is strictly JBoss configuration. It has nothing to do with LiveCycle.