Built, not switched on yet. DocFila cannot update Salesforce records yet. The connection and the update step are built, but they need a Salesforce connected app, which DocFila does not have.
Send a document for signature from DocFila and attach the signed PDF to the record yourself.
There is no single Integrations screen. Cloud storage is in Settings › Cloud Sync and in a team workspace's Connectors tab. Slack, Gmail and Salesforce sign-in is in an organization's Settings. Accounting exports are in FinFlow › Reports. Outbound webhooks are an action in Tools › Workflows.
Keep going with the document workflow that matches this page. Open the tool you need, then finish the file in DocFila.