I assume that you have already setup eclipse juno.
Go to http://tomcat.apache.org/download-70.cgi and download the Windows Service Installer.
Execute the installer exe file and go through it like this:
Choose “normal” type to install.
Configure your Tomcat with this adjustment.
Select your JRE.
Choose install location & click install.
When Tomcat installation completed open your eclipse IDE. Then open “Window” -> “Preferences” a new dialog will open.
In this dialog you should navigate to Runtime Environments.
Choose your tomcat version (v.7.0) and click “Next”.
Then maintain a name and the tomcat installation directory.