To set up OneDrive on portal.office.com, first, go to the website and log in with your Microsoft account credentials. Once logged in, you'll be directed to your Office 365 dashboard. Look for the OneDrive icon, usually found in the app launcher (grid of nine dots) at the top left. Click on it, and OneDrive will open in your browser. If its your first time using it, follow the on-screen prompts to complete setup, including syncing your files. You can also download the OneDrive desktop app for easier file management across devices. Access OneDrive anytime by returning to portal.office.com.