Adds necessary README step

Author: pufi656

README.md

@@ -34,10 +34,11 @@ With the input streams, mitigations, and vulnerabilities for the executable to e
 1. Ensure you have Docker installed.
 2. Install the required Python 3 packages via `poetry install --no-dev`.
 3. Build the Docker image: `docker build --tag zeratool_lib -f docker/Dockerfile.zeratool_lib .`.
-4. Ensure the Docker API is accessible by:
+4. Add `zeratool_lib` to PYTHONPATH: `export PYTHONPATH=/path/to/repo/docker/zeratool_lib/zeratool_lib`.
+5. Ensure the Docker API is accessible by:
    - Running the module as `root`; or
    - Changing the Docker socket permissions (unsecure approach) via `chmod 777 /var/run/docker.sock`.
-5. Build the arguments' adapter via `cd others/argv_adapter && make`.
+6. Build the arguments' adapter via `cd others/argv_adapter && make`.
 
 ## Development