Create an "olatdata" folder (e.g. in your Eclipse workspace), its path will be further referred into the userdata.dir parameter of the olat.properties file.

Create an empty create an empty olat.local.properties and save it to /yourTomcatDir/lib (OLAT searches for this file on the classpath and /tomcat/lib is part of it). But OLAT should start with just the default config (empty olat.local.properties) !