1. Open the Eclipse (Juno Version), click on Help table, select the Eclipse Marketplace ->
2.
Now now type the 'Maven' enter, you can see maven related software's, you can select the 'Maven Integration for Eclipse' and select the 'install' button and accept the license. Once the installation done it will ask you to restart say yes. You are good to go with Maven integration with Eclipse.
3.You can even manager (install/uninstall) other tools/software's integrations like SVN,Spring tool suite,Android development tools,Jboss tools ...etc.
4. you can also move to other Marketplaces with in the market place window, like Yoxo,Obeo,BREDEX,Eclipse. Eclipse Marketplace is the default one.
Good luck!.