(Edit 2016-10-12: Many Eclipse downloads from https://eclipse.org/downloads/eclipse-packages/ have M2Eclipse included already. As of Neon both the Java and the Java EE packages do - look for "Maven support")
Way 1: Maven Eclipse plugin installation step by step:
At pop up: fill up Name as "M2Eclipse" and Location as "http://download.eclipse.org/technology/m2e/releases" or http://download.eclipse.org/technology/m2e/milestones/1.0
Now click OK
After that installation would be started.
Way 2: Another way to install Maven plug-in for Eclipse by "Eclipse Marketplace":
After successful installation do the followings in Eclipse:
Finally,