To follow an iCal feed on an iOS device, the basic procedure is to acquire the iCal feed URL from the website, then add it to the saved feeds on your device.
Getting an iCal link
To find the iCal URL for a particular calendar, select the "Feeds" icon in the top-right corner of the Calendar element.
Note: If this icon is not visible, ensure that the "Display alerts and feed controls" checkbox is selected in the Calendar element.
In the "Calendar Feeds" window that pops up, hover over the green "ICAL" button and select "Get Standard iCal URL."
If you perform this step on your iOS device, then you can long-press this URL to "Select All" and copy it to the clipboard. If you cannot perform this step on your device, obtain the link on your computer, email or text the URL to your mobile device, and then copy the URL on your device.
In either case, you should end up with the iCal feed URL on your clipboard.
Adding an iCal subscription to your device
Once you have copied the feed URL, add it to your mobile device by following the instructions from Apple.