Open Google Drive and create a new Google Sheets from Google Drive.
You can also open existing Google Sheet.
Click on the Share button in the upper right corner. In the people field put in the email address that you copied from Save Service Account Email and click on Done.
Take the ID part from the https link of the spreadsheet. The sheet ID can be found in the URL of your google sheet, for example in https://docs.google.com/spreadsheets/d/1eMwVSUK-vXWleH8YDLVH655ktRY_Ny0zHZxkzWxt1Jk/edit#gid=0. The ID would be 1eMwVSUK-vXWleH8YDLVH655ktRY_Ny0zHZxkzWxt1Jk.
This information will be used to Set up Google Sheet Connector.