--- a/README
+++ b/README
@@ -25,6 +25,10 @@ files that this program would delete use
How to install
==============
+Obviously you need an installed version of Mercurial to use this extension.
+"purge" has been tested with Mercurial 0.8.1 and 0.9 but it may work with
+other versions as well.
+
Put the "purge.py" file in a directory of your choice. Enable the extension
inserting an instruction like "purge=/path/you/choose/purge.py" in the
"[extensions]" section of a configuration file read by "hg".