You can edit the contacts from your PC without the need to install anything. Connect your phone to WiFi, then go to Settings > Accounts > Google. Tap on the default account, then tap on Sync Contacts. Wait for the process to complete (sync activity will stop).
Open a browser, then go to Google Contacts and log-in with the account attached to your phone. Edit the contacts, then SYNC them with the phone again and that's it. You can add pictures, edit fields, notes, etc.