Here are the steps to add Cucumber plugin to eclipse easily and hassle free.
Prerequisites: Java & Eclipse should be installed with proper environment variables configuration.
1. Open Eclipse
2. Click on Help in Menu bar
3. Select Option Install new software
4. Enter "http://cucumber.github.com/cucumber-eclipse/update-site" in "Work with" field (Point 1 in Screenshot below)
5. Select checkbox (Point 2 in Screenshot above)
6. Click Next/Finish/OK depending on eclipse version(Point 3 in Screenshot above)
And It's Done. Happy Testing!