Sorry I didn't answer this sooner! Did you mean the first comic from that story arc? Or the first comic ever? The Archives page has a listing by story arc or year. The front page has a First button to take you to the very first comic ever.
I'm in the process of slowly revamping parts of the site to make it more easy to navigate - not easy to do with ten years of archives - but adding button to the start of a story arc is a great idea. I may implement that!
Thanks for reading!