...
Create a Google API Project by clicking on Select a project, and then the New Project button in the dialog. Provide it a name such as JIRA Google Sheets Integration. You will need to log in with the Google Account that you want the Google Sheets to be associated with.
Now create a Google API Service Account and associate it with the project created above. Click the Create Service Account button at the top of the screen to start the creation process.
...
On the Create service account screen that is displayed, provide a name for your service account, and a description. These values should accurately describe what the account will do, but are not critically important. When you are finished, click the Create button below the description input to move the service account grants step (2).
On the next screen, click in the Select a role area to display the role selection dialog. Give your new service account a role of Project->Owner.
After selecting the appropriate role, click on the Done button at the bottom of the screen to finish creating the service account. The Grant users access to this service account step can be skipped.
You will be returned to the Service accounts listing screen and the account you just created will be visible. In the Actions column on the far right for your account's row, click on the actions icon and select the Manage keys option.
In the key screen, find the Add Key drop down and select Create new key option.
In the create key creation dialog that appears, tick the radio button for the JSON key type, and then click the Create button.
...
Click the Closebutton at the bottom right of the dialog to and return to the service account listing screen by clicking the Service Accounts navigation item on the left side. You should now see your new service account and key ID listed with a green checkmark check mark in the Status column. Please contact us if something does not look correct.
...