At Admin Panel -> Settings -> Switches you'll find a "show statistics area" option among the template switches. When on, this displays a small statistics box on the front page of the site. It displays the total number of topics, posts, members and clicks along with the time of the last update and a welcome message for the newest member.

To customize the look or content, go to Admin -> Themes -> Manage Templates -> "Front Page" and find <IF {SWITCH_STATSAREA}>... edit the box below that. If you have a multilingual site, most of it is in the language item main_statsstuff (which you can search for at Admin Panel -> Customizations -> Language).