Explain that secure boot should be disabled to run

the etherlab kernel module.
Show how to check if secure boot is enabled or not and
explain how to disable it.

ethercat_driver_ros2/sphinx/quickstart/installation.rst

@@ -8,6 +8,33 @@ Installing EtherLab
 The proposed development builds upon the `IgH EtherCAT Master <https://etherlab.org/en/ethercat/>`_.
 Installation steps are summarized here:
 
+* Verify that you can run unsigned kernel modules
+
+Etherlab is a kernel module that is not signed by default. To allow the kernel to load unsigned modules, you need to disable secure boot. 
+
+Verify if secure boot is enabled (you need to install ''mokutil'' first):
+  .. code-block:: console
+
+    $ sudo apt-get install mokutil
+    $ mokutil --sb-state
+
+it should print:
+  .. code-block:: console
+
+    SecureBoot disabled
+
+if it prints:
+  .. code-block:: console
+
+    SecureBoot enabled
+
+Then you need to disable secure boot.
+To do so, 
+
+  1. reboot your computer and enter the BIOS settings. 
+  2. In the security tab, disable secure boot. 
+  3. Save and exit.
+
 * Install required tools:
 
   .. code-block:: console