macOS
If you would like to change the login password on your OIT issues macOS computer please see: https://support.apple.com/guide/mac-help/change-the-login-password-on-mac-mchlp1550/mac
Windows
Most OIT issued Windows computers are on the domain which means your password is synced with you Williams/Okta password. To change the password on your Williams account see: https://oit.williams.edu/help-guides/accounts/williamsokta/#change-your-current-password