Apple seems to have removed the feature that allows you to import an iCal file into the Calendar App on iPhones and iPads. You can still import iCal files into the Calendar app on your computer (Mac) and it will show up on your phone if you have your computer synced to your phone via iCloud.
The alternative is to try to email yourself the iCal file (once it's been uncompressed) and see if the Mail will acknowledge the file and give you the option to add the events it to your calendar. It might work automatically once you open the email.
If that doesn't work, you'll have download Google Calendar to your phone. You will have to go to Google Calendar via your web browser on your phone. Andfollow the instructions here.