Update README.md

README.md

 # Installation
 
-Download the last RTKLIB version [http://www.rtklib.com/](url)
-an save it in your home directory (/home/user-name).
+Clone the repository in your chosen directory. In a new terminal:
+
+```
+cd <your/path>
+git clone <repo-link>
+```
 
 Create a directory to build all the source files:
 ```