Add info on Pypi availability

Author: ilikecake

README.rst

@@ -52,8 +52,28 @@ or individual libraries can be installed using
 
 Installing from PyPI
 =====================
-.. note:: This library is not available on PyPI yet. Install documentation is included
-   as a standard element. Stay tuned for PyPI availability!
+On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally `from
+PyPI <https://pypi.org/project/circuitpython-i2c-expanders/>`_.
+To install for current user:
+
+.. code-block:: shell
+
+    pip3 install circuitpython-i2c-expanders
+
+To install system-wide (this may be required in some cases):
+
+.. code-block:: shell
+
+    sudo pip3 install circuitpython-i2c-expanders
+
+To install in a virtual environment in your current project:
+
+.. code-block:: shell
+
+    mkdir project-name && cd project-name
+    python3 -m venv .venv
+    source .env/bin/activate
+    pip3 install circuitpython-i2c-expanders
 
 Installing to a Connected CircuitPython Device with Circup
 ==========================================================