There are a number of ways to view archived strips, but here is the most direct way: first go to www.gocomics.com click on the comic you want to view the archive for.
Once the comic loads, look below the comic for your archive (calendar) button. You can either click the date to open up the calendar tool, or you can use the "left and right" arrows to go back or forward in time if you're only searching for a recent date.
Alternatively, if you're unaware of what date you're wishing to view for a particular feature, you can use AMU Reprints, which has a more robust search function.