You will find the program as a menu item in SSMS, along with SQL Prompt if you use it. There is an issue so if the menu item is greyed out read below...

The issue you are experiencing with SQL Refactor and SQL 2005 SP2 where the Refactor menu is greyed out is a known problem with SQL 2005 SP2. There is a beta fix for this problem available - this can be downloaded from the following location:

ftp://ftp.red-gate.com/SQLRefactorBeta/sqlrefactorsetup.exe

There will be an official release of Refactor which will include this fix shortly, however hopefully this beta will solve the problem you are experiencing in the short term. Please keep an eye out for this official release.