If you already have it installed.. Now go to your desired page>> add to main (or sidebar)>> add block>> scroll to the bottom of the list and you'll see the latest installed add-on (Calendar)>> add it to the page.

I haven't personally used it but I'm guessing you could use a custom template. You'd select your custom template after adding the block to the page. Click on the block and select 'Custom Template' from the list.

Here is an iCal calendar template-
http://www.concrete5.org/marketplace/addons/ical-template/...