Hi, JOYCE MCDOUGALL
Thanks for choosing Microsoft Community.
Learn that you want to know how to install Defender on your phone and laptop.**If you want to install Defender on your laptop, you can follow the steps below.**Windows:
Simply launch it from the Start menu (or click the link below) and sign in with your personal Microsoft account for Microsoft 365.
microsoftdefender://
Mac:
Open https://aka.ms/MacDefender on your device to download the WDAV.PKG installation file.
https://aka.ms/MacDefender
Open the WDAV package file on your Mac and follow the installation steps.
After installation, sign in using the personal Microsoft account associated with your Microsoft 365 subscription (for example, @outlook.com, @hotmail.com, or @live.com).If you want to install Defender on your phone.
You can scan the following QR code.

Or search for Microsoft Defender in the App Store.
For more specific information, please check this link.
Installing Microsoft Defender - Microsoft Support
If you have any other concerns or questions, please ask and we will do our best to help you.
Best Regards,Kyra – MSFT | Microsoft Community Support Specialist