In your Comic Settings (in the Edit Comic area) there's an option to enable the "Homepage" for your comic:
It's pretty simple really. If you enable it, then people who visit your comic will be taken to the FIRST page in your archive, rather than the LAST (or most recent). This is especially useful in a few cases:
However, remember that your visitors will always be taken to the first page, even if they've visited before. That means even if a regular reader sees your comic has updated today, when they visit your comic they'll see the first page. Then they have to use the archive dropdown or the navigation buttons to reach the most recent page. So, some readers find the use of homepages annoying. You should consider carefully before you enable it.