Update README.md

README.md

@@ -35,7 +35,7 @@ If you have a problem at compile time it may be due to a bad configuration of yo
 
     #f_gnuplot to draw values of blc_channels
     brew install gnuplot --with-qt
-    git submodule update --init 
+    git submodule add  git submodule add https://framagit.org/blaar/f_gnuplot.git
  
  
     #f_view_channel to have a gtk interface to view blc_channels (need gtk3, blgtk basic library for gtk3,  will be installed)