add proper cloning instruction

README.md

@@ -6,6 +6,11 @@ This repository contains all presentations related to R3.
 
 <img src="https://webdav-r3lab.uni.lu/public/R3lab/logos/warning.png" height="20px" width="20px"> Install Docker first: https://docs.docker.com/install/
 
+<img src="https://webdav-r3lab.uni.lu/public/R3lab/logos/warning.png" height="20px" width="20px"> Please clone using the following command:
+```bash
+$ git clone --recurse-submodules ssh://git@git-r3lab-server.uni.lu:8022/R3/outreach/templates/presentation.git
+```
+
 Then, run:
 
 ```