Add 'usage' section to the getting started documentation (#379)

Extend the getting started section by providing some usage examples.

Closes #374

doc/source/index.rst

@@ -51,16 +51,14 @@ optimization of composite structures.
             Guides on how to achieve specific tasks with PyACP.
 
         .. grid-item-card:: :octicon:`play` Examples
-            {% if not skip_gallery %}
-            :link: examples/index
+            {% if not skip_gallery %}:link: examples/index
             :link-type: doc
             {% endif %}
 
             A collection of examples demonstrating the capabilities of PyACP.
 
         .. grid-item-card:: :octicon:`file-code` API reference
-            {% if not skip_api %}
-            :link: api/index
+            {% if not skip_api %}:link: api/index
             :link-type: doc
             {% endif %}
 

doc/source/intro.rst

@@ -16,4 +16,105 @@ because it keeps Python packages isolated from your system Python.
 Usage
 ^^^^^
 
-TODO
+Start ACP
+~~~~~~~~~
+
+Start a Python interpreter and import the PyACP package:
+
+.. code-block:: python
+
+    import ansys_acp.core as pyacp
+
+
+Next, start an ACP instance:
+
+.. code-block:: python
+
+    acp = pyacp.launch_acp()
+
+Load a model
+~~~~~~~~~~~~
+
+To load a model in ACP, use the :meth:`import_model <.ACP.import_model>` method:
+
+.. code-block:: python
+
+    model = acp.import_model(path="path/to/model.acph5")
+
+This can be either an existing ACP model (``.acph5`` format) or an FE model.
+When an FE model is loaded, the format needs to be specified:
+
+.. code-block:: python
+
+    model = acp.load_model(path="path/to/model.cdb", format="ansys:cdb")
+
+See :class:`.FeFormat` for a list of supported FE formats.
+
+
+Start modelling
+~~~~~~~~~~~~~~~
+
+Start defining new objects in the model. For example, to create a new modeling group and modeling ply:
+
+.. code-block:: python
+
+    modeling_group = model.create_modeling_group(name="Modeling Group 1")
+    modeling_ply = modeling_group.create_modeling_ply(name="Ply 1", ply_angle=10.0)
+
+These ``create_*`` methods take additional parameters, which can be used to immediately set the properties of the new object.
+For example, refer to the documentation of :meth:`create_modeling_ply <.ModelingGroup.create_modeling_ply>`.
+
+Alternatively, you can always set the properties of an object after it has been created:
+
+.. code-block:: python
+
+    fabric = model.create_fabric(name="Fabric 1")
+    modeling_ply.ply_material = fabric
+
+.. hint::
+
+    When using PyACP from an IDE, you can use autocompletion to explore the available methods and properties. PyACP provides type hints to make the autocompletion as helpful as possible.
+
+
+Save the model
+~~~~~~~~~~~~~~
+
+To save the model, use the :meth:`save <.Model.save>` method:
+
+.. code-block:: python
+
+    model.save("path/to/saved/model.acph5")
+
+
+Update and plot the model
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To update the model, use the :meth:`update <.Model.update>` method:
+
+.. code-block:: python
+
+    model.update()  # Note: our model is still incomplete, so this will raise an error
+
+
+Many PyACP objects provide data which can be plotted. For example, to show the mesh:
+
+.. code-block:: python
+
+    model.mesh.to_pyvista.plot()
+
+
+Or to show the thickness of a modeling ply:
+
+.. code-block:: python
+
+    modeling_ply.elemental_data.thickness.get_pyvista_mesh(mesh=model.mesh).plot()
+
+
+Continue exploring
+~~~~~~~~~~~~~~~~~~
+
+This is just a brief introduction to PyACP. To learn more:
+
+- Check out the `examples <examples/index>`_ to see complete examples of how to use PyACP.
+- The `how-to guides <howto/index>`_ provide instructions on how to perform specific tasks.
+- The `API reference <api/index>`_ provides detailed information on all available classes and methods.