Same place. You can either add it into the extra_copyright
phrase, which will show up at the bottom of you site, under the XF copyright, or you can add it wherever you want it to display in the PAGE_CONTAINER
template. Again, if it were me, I'd just go the phrase route because, honestly, that's where I'd put it in the template anyways and editing the template could just cause extra steps on upgrade (merging templates, for example).
To add it into the phrase, go to the admin control panel, navigate to Apperance -> Phrases. Search for, and click on, the extra_copyright
phrase. Add that code into the phrase text
box, and save.