The iPad does not have a standard app that will read .ics files. There are some apps in the App Store that will. I have no experience with them, so I won't make recommendations. Search for "ics calendar".
Don't overlook the iPhone apps. While they won't look as good on the iPad, they should work. I noticed one (the cheapest that looked like it might work) called Calendar Happy. It says it will import ics files to the standard Calendar app. This may be all you need/want.