Visio is not bundled with the Mac version of the Office package. In this case, you have two options: an alternative or Windows emulation which allows you to install Microsoft Office. For alternative, I recommend LucidChart. It's an online service which practically emulates Vision from top to bottom plus extra features. If you prefer Windows emulation, you can go with Bootcamp (the pre-built feature which allows Windows installation next to Mac OS installation) or Parallels Desktop which lets you run Windows inside Mac OS giving you access to Windows applications with a switch of a button.