Program settings (also known as Preferences) are available in three locations:

Program settings are divided into two sections. Click Settings in the menu panel to access settings, as shown here.

You will note that General is highlighted in blue, indicating it is the selected settings group. Available settings are:

The My Account tab has two variations. The first variation is for Free or Trial users. It offers the opportunity for the user to purchase a license, or to enter a license which they have already purchased. The screen is shown here.

If they are using the Premium version of Malwarebytes, a slightly different screen is shown. This version takes into account that they have already purchased a license, and the two buttons at the bottom are replaced with the Change License Key button.