I have my laptop setup to ask a password at POST... setup thru the BIOS. But if you don't want to do that, with ArcaOS you can right click on the desktop, choose 'Properties', then click on the 'Screen Saver' tab. Check 'Screen Saver Enabled',,'Use Password Protection', enter your password, and check 'Start Screen saver on system startup'. This will boot the computer to the screen saver, and require a password to turn it off.
Regards,