How can i replace the rear quarter window seals on my Ford Ka?

I have bought replacement seals for the rear windows on my 2000 reg. Ford Ka as they were leaking badly. Now that i've got them i don't know how to remove the old ones and replace them with the new ones. I've looked in my Haynes manual but no help there.
Any ideas re. removal and sealant that might be required would be gratefully received.
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