I see questions on the WordPress support size about changing the size of the window a tour is displayed in. Thought I would demo it, just for fun.
To do this I normally just use the “Short Code” section “Embed code with ID”.
I’m not sure, but you may want to leave the settings in “General” checked for “Auto height” and “Auto Width”, but this may over ride them anyway.
You can see this defaults to a window width of 560 pixels by 315 pixels. That makes the window look like this:
Inspecting the page shows that indeed it is a 560×315 size.
Changing the Embed shortcode to now be 760×215 we can see the effect on the display size.
Again, we can confirm the actual display size in comparison to the first window.
So, I think it is about that easy to set the initial display size.