update README

README.md

@@ -15,6 +15,7 @@ This repository is where the EBRAINS Spack packages are maintained. It contains:
 - the latest EBRAINS [Spack environment](https://spack.readthedocs.io/en/latest/environments.html) ([spack.yaml](spack.yaml)), a list of the specific versions of EBRAINS tools that are part of the software release
 - a script ([install_spack_env.sh](install_spack_env.sh)) that can be used to install the latest spack environment on any machine (either install from scratch or update an existing installation)
 - CI/CD pipelines configured for (a) testing the installation of new packages and (b) deploying the environment to the EBRAINS Collaboratory Lab.
+- (WIP) all the site-specific configurations that have been used to install the EBRAINS Spack environment in different systems, such as the EBRAINS Lab and the Fenix HPC systems.
 
 ## Contributing
 
@@ -42,9 +43,8 @@ Clone Spack. We currently use version v0.18.1:
 git clone --depth 1 -c advice.detachedHead=false -c feature.manyFiles=true --branch v0.18.1 https://github.com/spack/spack
 ```
 
-Modify (if needed) and copy the package.yaml file (that contains important package settings for Spack) and activate Spack:
+Activate Spack:
 ```
-cp ebrains-spack-builds/packages.yaml spack/etc/spack/packages.yaml
 . spack/share/spack/setup-env.sh
 ```
 
@@ -53,14 +53,21 @@ Add the project repository to your Spack environment:
 spack repo add ebrains-spack-builds
 ```
 
-Create and activate the environment:
+Create the environment:
 ```
-spack env create ebrains-env ebrains-spack-builds/spack.yaml
-spack env activate ebrains-env
+spack env create -d ebrains-spack-builds/
 ```
 
-Install:
+Define your site-specific configurations:
 ```
+export SYSTEMNAME=<your-system-name>
+mkdir ebrains-spack-builds/site-config/$SYSTEMNAME
+# copy any site-specific .yaml files inside the new dir
+```
+
+Activate the environment and install:
+```
+spack env activate ebrains-spack-builds
 spack install --fresh
 ```