To install blue, you should download the latest ZIP file from the blue Sourceforge page here . Unzip the file to a location of your choice. After unzipping, locate the bin folder and use either the "blue" script or "blue.exe", depending if your are on Linux/OSX or Windows.
Note: After starting blue, you may want to explore the example projects and pieces found in the blue\example folder.
The section below has notes for individual platforms.
Unless you are using a mouse that emulates a second mouse button, you will have to use a combination of the "open apple" key plus a mouse click for all "rt-clicks" that are mentioned in this documentation.
To make use of the function key shortcuts (F1-F12), you will also need to tick System Preferences, Keyboard and Mouse, "F1-F12 to control software features". (This affects recent versions of OSX.)