It appears that you can not add a site map to Google's BlogSpot.
You must have access to their server and that's not likely to happen in our life cycle.
Here's a link to
BlogSpot Help about the site map problem with google's BlogSpot that is dated 11/22/07
You might try a search in their "Help" section and with a bit of luck find something that will lead you in the right direction.
Life is grand
RT...