Check out the documentation on http://www.apache.org
There you'll find examples of apache and tomcat configurations and how to combine both.
JDK is probably installed in /usr/java
Tomcat may be installed in /usr/java/tomcat or something.
Maybe you can also find some documentation in the Tutorials sections of this forum, on http://tldp.org
or on similar sites (search this forum or use Google to find them).
You should set CATALINA_HOME and JAVA_HOME variables. I recommend putting them in the system profile or bashrc files in /etc, so that they are set for all users.