[plt-scheme] trouble installing simply scheme language to drscheme

Here is what I do:
run this code :
(require (planet "simply-scheme.ss" ("dyoo" "simply-scheme.plt" 1 2)))
then exit drscheme (it asks whether to save any changes,and I say
no),then start the program again.

When I check the language menu,I don't see a choice called "Simply
Scheme".
What am I doing wrong?