Visual Workflow is available in Enterprise, Performance, Unlimited, and Developer
Editions. The requirements are as follows:

• Windows Internet Explorer versions 8 through 11 (6 and 7 are not supported), Google Chrome, or Mozilla Firefox
• Adobe Flash Player Version 10.1 and later, the minimum version required to
  run the Cloud Flow Designer is 10.0
• A minimum browser resolution of 1024 x 768