There are no built-in options in the free version of the plugin for customizing the appearance, but I built it in a way where it’s easy to modify these things with a bit of CSS.
I’m using percentage sizes for everything, so it’s easy to scale up or down. If you want to bump up the text size of everything in the calendar you could just try something like this:
.ics-calendar { font-size: 120%; }
You may need to adjust somewhat to get exactly what you need. If you only want to change the size of certain elements you just need to narrow down to those. I’d recommend doing a View Source or Inspect Element in your browser to identify the CSS classes being used on the elements you want to change.
