Ok first you select "link to this Photo in Picasa
then you select the size you want to display
then copy what is displayed in the "embed image" field
go to tSkoolie.net and open your reply to post window, click on the IMG button on the top bar and then Paste the link in between the "[img][/img"
remove everything after the .JPG make sure at the end it still has the [/img]
do the same in front of the HTTP:// leave only the [img]
so that all what you have left is something like this
then click on Preview and see how your post will look like
something like this
If you did all this and it still does not work, then my guess is that you didnt make your picture album "public" on Picasa and hence no one except you can see the picture.
there might be quicker ways to do this but it works for me, someone else might have some other suggestions.