In-house customers: http://<your frevvo server domain name>/google/consent
Click Allow if you see a screen like the one below (Google often updates their UI so this may differ from what you see).
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Copy the access token. Save it to a safe location, you will use it when configuring your forms/workflows.
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Note
You must obtain a Google access token for every Google Account you wish to use with your forms/workflows. Repeat steps #1-4 above for each Google Account.
In-house customers with multiple servers must obtain Google Access Tokens for each server / Google Account.
Google limits the number of access tokens per Google Account. If the token limit is exceeded, older refresh tokens stop working.
Google may revoke Access Tokens unused for ~6 months. If this happens you must obtain a new new token and update your forms/workflows.