pre-warn users that the execution directory is important.

README.rst

@@ -33,6 +33,8 @@ To install, for example, the ``foss2022a-serial`` toolchain:
 
      $ cd /home/user/mpsd-software
 
+   Future calls of the `mpsd-software` command need to be executed from this
+   "mpsd-software-root" directory.
 
 .. comment:
     3. Initiate the installation at this location using::