Update.md

@@ -15,7 +15,7 @@ git pull origin master
 update the installation with
 
 ```bash
-./install -i "where you put the dependencies" -c "--prefix=where you want to install OpenFPM"
+./install -i "where you put the dependencies" -c "--prefix=where you want to install OpenFPM previously"
 ```
 
 complete the update with