hackathons/USW24: Add Session 03 - Behind the Scenes

Signed-off-by: Stefan Jumarea <[email protected]>

content/hackathons/usw24/index.mdx

@@ -127,3 +127,13 @@ While you work on them, mark the progress [here](https://docs.google.com/spreads
 After you are done with all of them, take a look to some more applications, following the tasks [here](https://docs.google.com/spreadsheets/d/1_dOqYnHKQgkVJn0Tiudawna4d1SV_PGgS1D8oLmGD34/edit?usp=sharing), and the same steps for building and running you used before.
 Go through them orderly and aim to complete all items until the Extra section.
 If you have extra time on your hands, go through the Extra section as well.
+
+### Session 03: Behind the Scenes
+
+In order to run applications using `kraft`, both locally and with `kraftcloud`, we need to build a minimal required filesystem for the application we want to run.
+We do that using `Docker`.
+This is useful both to understand what is happening behind the scenes and to have a test environment for your application.
+In case there are issues with KraftCloud / KraftKit, you can use Docker to see if everything is in the right place and to assist in debugging.
+
+Follow the steps [here](https://unikraft.org/docs/contributing/adding-to-the-app-catalog) to see how you can port a new application on top of Unikraft.
+Mark the items as completed [here](https://docs.google.com/spreadsheets/d/1_dOqYnHKQgkVJn0Tiudawna4d1SV_PGgS1D8oLmGD34/edit?usp=sharing).