Update README.md

Added instructions to install under MacOS X

README.md

@@ -1,2 +1,46 @@
-# pymol-install
-PyMol installation instructions
+# PyMol installation instructions
+
+## Installation under MacOS X
+
+Follow this steps to install a pre-compiled Open-Source version of [PyMOL](https://pymol.org/2/) under MacOS X.
+
+Tested under OS X 10.10, 10.11 and 10.12.
+
+1. Install [Homebrew](https://brew.sh/):
+```
+/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+```
+
+2. Install PyMol dependencies using Homebrew:
+
+```
+brew install Caskroom/cask/xquartz
+brew install tcl-tk --with-threads --with-x11
+brew install python --with-tcl-tk
+```
+3. Install PyMol:
+
+```
+brew install homebrew/science/pymol
+```
+
+4. Create an application alias for PyMol:
+
+- Open the Automator app, which is install per default in OS X.
+- Create a new document and select "Application".
+- Left under "Actions Library" select "Utilities" and "Run Shell Script".
+- Choose "/bin/bash" as a shell.
+- Paste the following: `/usr/local/bin/pymol -M`. Change the path to pymol (`which pymol`) if necessary.
+- Save the application ("File > Save") to the Desktop and name it "PyMol".
+
+5. Done, now you can start PyMol by double clicking the created application in the desktop.
+
+### Troubleshooting
+
+You might get an error when trying to start that says "Reason: image not found", regarding the library "Glew" not being found. This is becaus ethe version of "Glew" that PyMol uses is different than the one installed from Homebrew.
+
+To solve this, you need to create a symlink with the name of the Glew binary needed by PyMol linking to the one installed in your computer, for example:
+```
+cd /usr/local/opt/glew/lib;
+ln -s libGLEW.2.1.0.dylib libGLEW.2.0.0.dylib
+```