Hi Charles,
The width of the overall template is fixed to 600px so there is not a way to change that. The block width in that help page is talking about the width of individual blocks and will only show up if there is more than one block in the row. If you want to change the width you can use the Free Style Editor instead. You can also clone your block editor template when you're done and then change the editor on the template to Free Style and change the width within that editor.
