Update README.md

README.md

@@ -9,9 +9,51 @@
 1. [Release notes](#release_notes)
 
 # How to compile
-- one
-- two
-- three
+- Clone the project:
+  ```bash
+  $ git clone https://github.com/tiiuae/FMO-OS.git
+  ```
+- Move to source folder
+  ```bash
+  $ cd FMO-OS
+  ```
+- Install NIX (you also can make it manually or use NIX-OS, then you may skip this part):
+  ```bash
+  $ bash .github/actions/build-action/install_nix.sh
+  ...
+  ...
+  [ 1 ]
+  Nix won't work in active shell sessions until you restart them.
+  ```
+- No you need to restart your session:
+```bash
+$ exit
+```
+- Reloging your session and go to the source folder again:
+```bash
+$ cd FMO-OS
+```
+- Check build targets:
+```bash
+$ nix flake show
+...
+...
+└───packages
+    └───x86_64-linux
+        ├───fmo-os-installer-debug: package 'nixos.iso'
+        ├───fmo-os-installer-debug-compressed: package 'nixos.iso'
+        ├───fmo-os-installer-public-debug: package 'nixos.iso'
+        ├───fmo-os-installer-public-debug-compressed: package 'nixos.iso'
+        ├───fmo-os-installer-public-release: package 'nixos.iso'
+        ├───fmo-os-installer-public-release-compressed: package 'nixos.iso'
+        ├───fmo-os-installer-release: package 'nixos.iso'
+        ├───fmo-os-installer-release-compressed: package 'nixos.iso'
+
+```
+- Build FMO-OS installer image (you need to have github ssh keys installed on your system):
+```bash
+$ nix build -L .#fmo-os-installer-debug
+```
 
 
 # Ghaf documentation links