You really should use it, if for no other reason than to remember it. You have to have a password to install any software or updates to the system (that's for your protection).
But, if you don't want to use it, even though you have to have it, open System Preferences, Users and Groups, click on the padlock icon, enter your password (see, you need it), and then Login Options and in the top box, labeled "Automatic login:" change it to the user you want automatically logged in. Now go back to the System Preferences screen and on the Security and privacy tab, General options, again click the padlock, provide a password, uncheck the "Require password..." box and the "Disable automatic login" box.
Done. You now have zero password protection, but you'll need to remember the password because it's still there (you have to have one) and you will eventually need it to install software/updates.