In Studio under File -> edit project properties there is configuration of log4j (version 1) - there are also some components for log4j logging in Talend Exchange.
This is for any Talend product the same. In case of ESB as we have Karaf instance available there is also karaf Pax logging system, which integrates the Talend log4j. Look at container/etc/org.ops4j.pax.logging.cfg where you can also configure loggers which can be then called from any bundle deployed in following way:
private final static Logger LOG = LoggerFactory.getLogger(MyService.class);
LOGGER.info("Service myservice audittrail: entering the pipeline");
....if you like the pure Java