Creating build using maven in eclipse

Hi i am new to java web development i have created a simple dynamic web project in eclipse now i want to create a build file using maven.
I have installed maven plugin in eclipse but unable to create build file so please help me.

Welcome to the Ranch.

We have a dedicated forum for build tools. I will move your question there for a better response.

thanks

You need to start over from scratch and create a new project. When you create a project, choose Maven | Maven Project. Then when you get to the list of archetypes, choose one of the webapp archetypes (such as org.apache.maven.archetypes:maven-archetype-webapp). After you create the project, copy all of your sources from the old dynamic web application project over to the appropriate directories in the new Maven webapp project.

This might also be helpful: http://www.sonatype.com/Support/Books/Developing-with-Eclipse-Maven

while creating builf file getting error

Unknown lifecycle phase "HelloWorld". You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>.

please help

You need to provide more information. Where did you specify HelloWorld as a lifecyle phase? It almost sounds as if your project is a Maven plugin project. Either that or you misconfigured a plugin within pom.xml. Knowing exactly where HelloWorld appears would help. If you are not sure, attach your pom.xml file.