Scan your computer for viruses: Once your new antivirus software is installed, you should run an initial scan for viruses and other malware.Restart your computer if required: If you were using other antivirus software that you uninstalled or a free trial of your new software, you will have to restart your computer for your new software to begin operating.Consent to the licensing agreement: To use the software you've installed, you will have to consent to the user or licensing agreement.A few antivirus programs come on DVDs or other physical media, and these will come with their own installation instructions. Download the antivirus software: Download and install your antivirus software on your Mac the same way you do any other type of program.Creating an account also will allow you to receive notifications of software updates. This will let you adjust various settings related to privacy, the devices you're protecting, your subscription, and your payment method. Consider creating an account: When you purchase antivirus software online, you will probably be asked to create an account.