maven2 is a wonderfully powerful system and makes development very easy. However, each time you need to do something, it can be a real pain to find what you need to do.
One of the things you often need is adding a file to your local repository, specifically when the library is not available in a public repository.
An example of how this can be done :
mvn install:install-file -DgroupId=be.mygroup -DartifactId=library -Dpackaging=jar -Dversion=1.2.2 -Dfile=library.jar