how to change the function of a specific key in photoshop

If you want to change the keyboard shortcut for one specific command or tool, then follow Ged’s advice and use the keyboard shortcut editor in Photoshop.

If you want to switch what a modifier key like Alt or Ctrl does everywhere within Photoshop, that is not something Photoshop can control. You may be able to change that at the OS level. The picture below is how that would work in macOS; because your post says you use Windows you can see if there is a Windows keyboard setting for this.

If you need some modifiers to be switched not throughout the whole OS but only within one application such as Photoshop, that might be possible with utility software from another company.