Merge pull request #194 from ESMValGroup/add_choices_for_installation

Add brief summary of possible ways to use ESMValTool

Author: SarahAlidoost

_episodes/02-installation.md

@@ -25,6 +25,24 @@ be found in the
 We will first install Conda, and then ESMValTool. We end this chapter by testing
 that the installation was successful.
 
+Before we begin, here are all the possible ways in which you can use ESMValTool
+depending on your level of expertise or involvement with ESMvalTool and 
+associated software such as GitHub and Conda.
+
+1. If you have access to a server where ESMValTool is already installed
+as a module, for e.g., the [CEDA JASMIN](https://help.jasmin.ac.uk/article/4955-community-software-esmvaltool)
+server, you can simply load the module with the following:
+~~~bash
+module load esmvaltool
+~~~
+After loading ``esmvaltool``, we can start using ESMValTool. Please see the [next lesson]({{ page.root }}{% link _episodes/03-configuration.md %}). 
+2. If you would like to install ESMValTool as a conda package, then this lesson
+will tell you how!
+3. If you would like to start experimenting with existing diagnostics or contributing to ESMvalTool, please see the instructions for 
+source installation in the lesson [Development and
+contribution]({{ page.root }}{% link _episodes/08-development-setup.md %}) and
+in the [documentation](https://docs.esmvaltool.org/en/latest/quickstart/installation.html).
+
 > ## Install ESMValTool on Windows
 >
 > ESMValTool does not directly support Windows, but successful usage has been