• Start the Group Policy Management application
• Drill down the tree
  • • Forest: (your domain)
    • Domains
    • (your domains)
• Right click on “Default Domain Policy” and select “edit”
• In the Group Policy Management Editor (that hopefully just opened) drill down to
  • Computer Configuration
  • Policies
  • Windows Settings
  • Security Settings
  • Account Policies
  • Password Policy

Notes:

Enabling password complexity means you must have one item from three of the following groups:

• Uppercase letters of European languages (A through Z, with diacritic marks, Greek and Cyrillic characters)
• Lowercase letters of European languages (a through z, sharp-s, with diacritic marks, Greek and Cyrillic characters)
• Base 10 digits (0 through 9)
• Nonalphanumeric characters: ~!@#$%^&*_-+=`|(){}[]:;”‘<>,.?/
• Any Unicode character that is categorized as an alphabetic character but is not uppercase or lowercase. This includes Unicode characters from Asian languages.

Changes to the group policy takes some time to replicate to all domain controllers. To speed it up, start up a command line prompt and execute:

gpupdate