Disabling password login on a Mac is a simple one or two step procedure. To do this, open System Preferences and change some settings in 'Users & Groups'. If you have FileVault enabled, you must first disable it before you can disable password login again.
Steps
Part 1 of 2: Disabling FileVault

Step 1. Click on the Apple icon
It's the Apple logo in the top left corner of the main menu.

Step #2. Click on System Preferences

Step 3. Click on the icon of 'Security & Privacy'
This looks like a house.

Step 4. Click on FileVault

Step 5. Click on the padlock
This can be found in the lower left corner of the window.

Step 6. Type in your password

Step 7. Click on Unlock

Step 8. Click Disable FileVault

Step 9. Click Restart and Disable Encryption
The Mac will restart.
Part 2 of 2: Disabling automatic login

Step 1. Click on the Apple icon
It's the Apple logo in the top left corner of the main menu.

Step #2. Click on System Preferences

Step 3. Click on the 'Users and groups' icon
This looks like the silhouette of a person.

Step 4. Click on the padlock to log in as an administrator
This can be found in the lower left corner of the window.
- Type your password.
- Click Unlock or press ↵ Enter.

Step 5. Click Login Options
You will find this in the left frame at the bottom.

Step 6. Click on the 'Log in automatically' drop-down menu

Step 7. Click on a user account

Step 8. Type in the password

Step 9. Press ⏎ Return
This user account is now set up to log in automatically without having to enter a password.