Top 5 Atom Packages : #1 Emmet
Installing atom:
Visit: https://atom.io/
Installing Emmet:
1) Visit https://atom.io/packages/emmet
Or
2) In atom editor, Goto File - Settings -Install and type 'emmet' in 'Search Packages' input box
Emmet Cheatsheet: https://docs.emmet.io/cheat-sheet/