The Desktop App works like a bridge between your Tally ERP and TallyDekho mobile App on your phone. Desktop App extracts tally data from your system and saves it as encrypted file on your google drive linked to your account and generates QR code for the mobile App to get connected.
No, you should start TallyDekho when you start Tally ERP. You can set time interval like in every two hours to sync your data to Google Drive. You can also chose to sync it manually. For that you should open TallyDekho App whenever you want and click on sync button in the app. It generally takes 5-10 minutes to upload data on google drive. Please make sure Tally ERP is open when data is being synced.