I've added you to the list. After you've clicked the green coloured "Edit this wiki post" link at the top of the post, you should get a sort-of-pop-up box, with two copies of the post side by side. If you click the button with the pencil icon labelled "edit this wiki" label, then you should be able to edit the version on the left, and the version on the right becomes a preview.
@tomnewsom - I had to add a category to save the changes... is that right?
PS - welcome @tom_w!