According to the version of MESA you have installed on your computer, you have to follow the right instructions notes.
|MESA Update instructions|
|1.01 to 1.1||Update from Mesa 1.0.1 to MESA 1.1|
|1.1 to 2.0.1||Update from Mesa 1.1 to MESA 2.0.1|
|2.0.1 to 2.1||Update from Mesa 2.01 to MESA 2.x.x|