Uploading a large PowerPoint file to Google Drive is fairly easy. First, sign into your Google Drive account. You'll see a plus sign on the top right corner of the page. Click on it, and select “Upload Files” from the menu. From there, select your PowerPoint file and click “Open.” The file will begin to upload. Depending on the size of the file, it may take a while to finish. You can view the progress of the upload in the lower right corner of the page. Once the upload is done, your file will be available in your Google Drive.