Adds instructions how to clone the repositories.

docs/developer/build/python.md

+---
+title: Building Python Modules
+summary: How to build Python modules of UNICADO.
+authors:
+    - Sebastian Oberschwendtner
+date: 2024-04-09
+---
+> :construction: tbd

docs/developer/cmake-presets.md

@@ -8,7 +8,7 @@ date: 2024-03-06
 ## Introduction
 If you don't know what **CMake** presets are, read about them in their [Documenation :octicons-link-external-16:](https://cmake.org/cmake/help/latest/manual/cmake-presets.7.html){:target="_blank"}.
 
-We provide as standard set of presets in :octicons-file-16: `CMakePresets.json` which gives you some reasonable defaults.
+We provide a standard set of presets in :octicons-file-16: `CMakePresets.json` which gives you some reasonable defaults.
 However, our assumptions may not apply to your build environment.
 So there is the option to provide a custom :octicons-file-16: `CMakeUserPresets.json` which can override certain options of our presets.
 Just make sure your preset inherits our defaults.

docs/developer/get-source-code.md

+---
+title: Get UNICADO Source Code
+summary: How to clone the UNICADO repositories
+authors:
+    - Sebastian Oberschwendtner
+date: 2024-04-09
+---
+The source code of **UNICADO** is grouped into different repositories.
+You can get an overview of which repository contains which topic [here](../modules/overview.md).
+Whenever one repository needs another repository, we include it as a *Git Submodule*.
+If you are not familiar with *Git Submodules*, please read their [Documentation :octicons-link-external-16:](https://git-scm.com/book/en/v2/Git-Tools-Submodules).
+
+## Get the Source Code
+The repository [:simple-gitlab: Unicado Package :octicons-link-external-16:](https://git.rwth-aachen.de/unicado/unicado-package) contains all necessary source code as submodules to get started compiling **UNICADO** and its installer.
+
+When you clone the repository for the first time use this command:
+
+=== "Gitlab"
+
+    ```{.sh .copy}
+    git clone --recurse-submodules git@git.rwth-aachen.de/unicado/unicado-package.git
+    ```
+
+=== "Phabricator"
+
+    ```{.sh .copy}
+    git clone --recurse-submodules ssh://git@unicado.ilr.rwth-aachen.de:2222/source/rUNICADO.git
+    ```
+
+    !!! note
+        *Phabricator* is deprecated it will be removed in the near future!
+
+Should the default branch not yet contain the submodules or you want to update the submodules afterwards, you can do that with:
+```{.sh .copy}
+git submodule update --init --recursive
+```
+
+!!! warning
+    Only proceed when all submodules could be checked out successfully. Otherwise the builds will not work!
+
+## Where to find what
+In the following instructions we assume, that you cloned the **Unicado Package** as described.
+That means, whenever we talk about building inside the *Aircraft Design* folder, we mean the submodule **inside** the **Unicado Package** repository.
+In general, you should find every mentioned directory or file in one of the submodules of the **Unicado Package**. :point_up:
\ No newline at end of file

mkdocs.yml

@@ -100,6 +100,7 @@ nav:
         - 'Linux': 'developer/build-environment/linux.md'
         - 'MacOS': 'developer/build-environment/macos.md'
         - 'MSYS2/MinGW (deprecated)': 'developer/build-environment/mingw.md'
+      - 'Get Source Code': 'developer/get-source-code.md'
       - 'Build':
         - 'C++': 'developer/build/cpp.md'
         - 'Python': 'developer/build/python.md'