To obtain certificate please do the following:
1. In IAM & admin go to Service accounts
2. Create a service account for the project that your cloud storage bucket is attached to
3. Name the account
4. For permissions select the role you want it to have (I made it a storage admin)
5. In the "create key" section, create a new key and choose the type P12
6. Copy the key ID and download the certificate file
7. In the core console go to More -> cloud accounts
8. Create a new cloud account. Name the account a unique name and choose Google Cloud from the drop down
9. Under certificate click browse and then select the downloaded certificate file
10. For ID enter the Key ID
11. For Project ID enter the ID of the project. This can be found using the certificate file name (it's everything before the Key ID in the certificate name)
12. For email enter the email of the service account. You can find that on the service account page in the Google cloud console
13. Save it