We support all common spreadsheet formats as long as they are within Google Drive or OneDrive:
- Google Sheets (sheet tabs with less than 700,000 cells)
- Excel files (various formats), CSV, TSV, OpenDocument (all not larger than 8MB)
If you want to connect to your local files, you have to sync them with Google Drive or OneDrive first. For Google Drive, you can use Google Drive Desktop or Insync. For OneDrive, use OneDrive Desktop.