To install Notepad++ go to: https://notepad-plus-plus.org/download
Brackets is an open source as well but it is also a cross-platform editor; it is available for Windows, Mac and Linux. It was founded by Adobe as a modern text editor for web designers and front-end developers. It has syntax highlighting, and it has a sizeble collection of extensions.
To install Brackets go to: http://brackets.io/