Update Readme.md

Readme.md

@@ -13,3 +13,26 @@ For structure of the sources, see [ProjectTree](ProjectTree)
 
 Note that every file within OS/K is written using spaces for tabulation, with each
 tabulation being 4 spaces long. 
+
+#### Compile from sources
+
+To compile this project from sources, you must first install the dependencies
+
+```
+apt update && apt upgrade
+apt install grub-pc dosfstools make nasm
+```
+
+You also need to have the [OS/K cross-compiler](https://www.os-k.eu/build-tools/cross-cc.tar.xz) in `/opt/cross-cc`.
+
+To compile for the first time, you must compile the whole project, in order to build the loop disk image :
+
+```
+make all
+```
+
+After that, you can use this to compile the kernel only :
+
+```
+make kaleid
+```