Merge branch 'update_readme' into 'master'

Update readme

See merge request germann_e/spack-psi!11

README.md

@@ -4,20 +4,16 @@ WIP
 
 [Official Spack documentation](https://spack.readthedocs.io/en/latest/)
 
-## How to use:
+## How to use on Merlin6
 
 ```bash
-# Where you want to install Spack e.g /scratch/$user
-cd $SPACK_INSTALL_ROOT
+source /afs/psi.ch/sys/spack-rhel7/spack/share/spack/setup-env.sh # can be also include in your .bashrc
 
-# Cloning and setting official Spack
-git clone https://github.com/spack/spack.git
-source spack/share/spack/setup-env.sh
+spack env list
+spack env activate -d <package> # e.g ffbidx all for whole software stack
 
-# Cloning PSI/merlin env and activate it
-git clone https://git.psi.ch/germann_e/spack-psi.git
-spack env activate -d spack-psi/env/merlin/<package> # all for whole software stack
-
-# Install env
+# Install env if local development, else skip
 spack install # -v for verbose
+
+spack load <package>
 ```