If you're on vBulletin 3, the importer is already in the XenForo package, and the vBulletin 4 importer is here.
When you're done, you should also redirect your vBulletin URLs to XenForo, whether it be using vBulletin 3, vBulletin 4, or vBSEO (requires this + one of the two).
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