Hello @Alexey
Unfortunately, there’s no ready-to-go solution. As independent integrator, you have to build your own integration. You can start with these titles: https://api.onlyoffice.com/editors/howitworks https://api.onlyoffice.com/editors/demopreview
They provide general information and some integration samples. The main point is that Document server is just an editor and you have to achieve the communication between your storage and Document server.
The other way is using ready-to-go integrations. For example, SharePoint or any others integrations.