In the Desktop Client go to Toolbox > Settings > Miscellaneous > Modify Password
If you FORGOT your password you can ask a colleague (or Admin) with sufficient permission to access your profile in the Object Manager and change your password.
Super Admins / IT with access to the farmerswife server (local hosted) can also change a password on the Server > Setup > Users Tab.
Web Users / Resources with Web Access
In the Application > Miscellaneous > Change Password
In the Web Client you can change your password from the three ...