To install Microsoft Office from portal.office.com, start by signing in with your Microsoft account. Once logged in, click on the “Install Office” button located on the homepage. Choose “Office 365 apps” from the dropdown to begin the download. After the setup file downloads, open it and follow the on-screen instructions to complete the installation. Make sure your device meets the system requirements and has a stable internet connection. Once installed, open any Office app (like Word or Excel) and sign in again to activate your subscription. You’re now ready to use Microsoft Office on your device.