To back up your data using OneDrive, open the OneDrive app and sign in with your Microsoft account. Drag and drop the files you want to back up into the OneDrive folder in File Explorer. The files will sync to the cloud, indicated by a green check mark. Once synced, you can access your files from any device by signing into OneDrive. Regularly update your OneDrive folder to keep your backup current. This ensures your data is protected and easily retrievable.