Exactly what do you mean by "placing a jar on the classpath of my Mavenised Project"? With Maven, you don't place JARs anywhere; instead, you add dependencies within your pom.xml.
Since you create the JAR, that information (also known as the artifact's coordinates) is up to you. Did you create it using Maven? If so, you have already the coordinates. If you did not use Maven, it might be best if you did, then you can build the jar using "mvn install" and then reference it in your project. (If you insist on not converting it to Maven, you can still use "mvn install:install-file" to load the jar into the local repository; you would given the coordinates as part of that command)