fix README.md

README.md

@@ -17,7 +17,7 @@ We call this extension BCovise and it has been developed at [IT4Innovations Nati
 
 # Building process
 * See https://wiki.blender.org/wiki/Building_Blender
-* Note: BCovise reuquires boost_iostreams linked with zlib
+* Note: BCovise reuquires boost_iostreams linked with zlib and set *COVISE_SRC_DIR* to [Covise](https://code.it4i.cz/blender/blender-covise).
 
 # Introducing Covise Nodes
 Covise nodes is a specific set of nodes designed for scientific visualization. They are part of the **Covise Editor** in Blender.