Start map in fullscreen mode
In your Joomla backend go to Menus -> Your Menu -> Your hotspots map link -> select it
In the settings you'll have a "fullscreen option". Set it to yes and the map should now load in fullscreen when the page loads.
If you have the resize map option in the global settings of the component set to yes -> users will be able to make the map small again. If on the other hand it is set to no, then users won't be able to resize the map.