Create Google Cloud Service Account Key File

After logging in to the console, you have to create a new Service Account Key and save the files. 

Go for the Credentials section of the API & Services page in the console. Then click on Create Credentials button.

This section will appear after clicking on Create Credentials.  Select Service Account.

Then provide all service account details. Like service account name, ID, description. After providing all these click on Create and Continue.

Click the Select a role dropdown. Choose “Storage Admin” after selecting “Cloud Storage” by Under product or service. Next3 Offload will be able to create buckets for you and manage the objects in the bucket if you have the Storage Admin role.

After completing click Done.

Click the newly created service account at the bottom from the Credentials page.  Click Keys, then select Create new key.