If you would like the logo to redirect to the homepage, go to your Acp->Options->Basic Board Information->Link Logo to Home Page URL. Like this the logo will redirect to whatever url you will have entered at Home Page URL setting.
If you would like the logo to redirect to another link instead, at the logo_block template find this code:
HTML:
<a href="<a href="{$logoLink}">
and change {$logoLink} with whatever url you would like the logo to redirect to when clicked upon. Hope it helps.