how may I uninstall messages on my computer. I would not like anyone using the computer to access my messages.

Set up separate user accounts on your Mac. One for each person who uses it. Sign out of your account or switch to the login screen when you walk away from it and don’t give anyone the password for your account. That way you can still use messages on your Mac, but no one else will be able to access them or any of your other personal data.

I would suggest making the other user accounts "Standard" user accounts which will limit what those other users can do. If those other user accounts are "admin" accounts, then they can theoretically access the main user's account. Anyone with "admin" access can do the exact same things as the original main admin user.