new file: instructions.md

src/docs/instructions.md

+# Instructions on building the athena detector geometry
+
+Instructions on how to setup your environment and run the full simulation.
+
+## Step 1: Setup a sandbox directory
+
+Create a local directory that you want to work in, e.g., `~/eic`
+```bash
+mkdir ~/eic
+cd ~/eic
+```
+
+## Step 2: Deploy the containerized environment and launc a shell
+
+Execute the following line in your temrinal to setup your environment in your sandbox
+directory. This will install the latest stable container and place a script called
+`eic-shell` in the top-level directory. This script will load the environment for you.
+```bash
+curl https://eicweb.phy.anl.gov/containers/eic_container/-/raw/master/install.sh | bash
+```
+
+Now you can launch a shell in our development environment:
+```bash
+./eic-shell
+```
+
+Note that this will also set the `$ATHENA_PREFIX` environment variable, and the related
+environment variables. You should install all local software to this `$ATHENA_PREFIX`
+(which is the `./local` subdirectory of your sandbox working directory).
+
+## Step 3: Clone the repos
+
+Right now there are 2 repos you need:
+* IP6 (IP-specific components)
+* Athena detector
+
+```bash
+git clone https://eicweb.phy.anl.gov/EIC/detectors/athena.git
+git clone https://eicweb.phy.anl.gov/EIC/detectors/ip6.git
+```
+
+## Step 4: Build/install the detector plugins
+
+We need to build detector plugins for both the Athena and for the IP.
+
+### Building IP6
+```bash
+cd ip6
+mkdir build && cd build
+cmake -DCMAKE_INSTALL_PREFIX=$ATHENA_PREFIX ..
+make install
+cd ../..
+```
+
+### Building the athena detector
+```bash
+cd athena
+mkdir build && cd build
+cmake -DCMAKE_INSTALL_PREFIX=$ATHENA_PREFIX ..
+make install -j8
+cd ../..
+```
+
+## Step 5: Link the compact files for IP6 
+```bash
+cd athena
+ln -s ../ip6/ip6
+```
+
+## Final Step 
+That's all, you are now fully setup. Let's try a simple geometry overlap check
+to make sure everything works properly.
+
+```bash
+checkOverlaps -c athena.xml
+```
+
+In order to run the simulation with our datamodel, you should use the `npsim` executable.
+You can exectute
+```bash
+npsim -h
+```
+to get help on how to do this. 
+
+Here is an example command for npsim with from a Hepmc3 file:
+```bash
+npsim --runType batch \
+      --part.minimalKineticEnergy 100 \
+      -v WARNING \
+      --numberOfEvents 100 \
+      --compactFile athena.xml \
+      --inputFiles YOUR_FILES.hepmc \
+      --outputFile YOUR_FILENAME.root
+```