To upload from Google Drive:
After clicking the yellow “+NEW” button in the top right corner of the datasets page, then selecting File Upload, select Google Drive. Next, you'll need to authenticate with your Google Account.
After signing in, you can select any files in Google Drive to import to Gigasheet. Keep in mind only supported files will be processed successfully.
See the How to Page for step-by-step visual instructions.
See this video for more information on uploading from google drive.