UBB.threads PHP Forum Software Community Forums UBB.threads 7 Importer Support Does the import add or replace?

Another site wants me to import all their information into my forum so that they will no longer have to admin their site. The site is in ip.board, but I think I can convert that to phpbb. Will the Threads phpbb importer append the content or do you have to use it on a clean install?

Thanks.