First u can create as a war Directory structure .
Like
Hello
|
|
WEB-INF
|
|---web.xml
classes
|
|-----HelloServlet.java
|-----HelloServlet.class
then u compile ur
java file using javac command
And enter ur
servlet entries at web.xml.
later u can create as a WAR using ---jar -cvf Hello.war Hello
Finally u can login admin console.
LeftHandSide u can see the Applications--->installNewApplication -->choose ur war file and define context root name like /Hello .
Then u can apply next until finish .