You must do two things:

* bonobo-activation-server (from now on referend as b-a-s), must be able to 
  find your .server file, it can be done in three ways:
  
   1) Copy the server to /usr/lib/bonobo/servers
   2) set BONOBO_ACTIVATION_PATH to the current directory, restart b-a-s
   3) activation-client --add-path $(pwd)
   
* bonobo-activation-server must be able to launch your applet, can be
  done in three different ways:

  1) add your current directory to PATH before restarting b-a-s.
  2) Copy applet.py to any directory in PATH
  3) Modify the .server file and change location to include full path
     to your component.
     
Both problems are related to bonobo-activation-server, a daemon which launches
bonobo components, an applet is a very simple bonobo components and must 
therefor be able to be found by the daemon.

Please note, that you might need to change the first line of the script, eg
the python interpretor you are using. If pygtk is not installed so it's used
by the default interpretor (the one called when typing just python) you have
to change the first line, change the path (/usr/local/bin/python) or the
name (python2.2).