If you are using a restricted user account (i.e. you are not a computer administrator) the Settings menu may be disabled.
The menu may also be hidden to prevent unauthorised changing of settings, in which case you can access the settings by pressing SHIFT+CTRL+F12 (i.e. all three keys at the same time)
Within the Settings menu you will find the Settings option, which allows you to change numerous settings for the software. This is covered within its own section of this user guide.