Iam not sure why are you trying to use CMIS connector for SharePoint Online (SPO). MicroSoft doesn't support CMIS in SharePoint Online.

Also it would be nice to understand the usecase that you are trying to realize but,

If you are trying to use SharePoint Online (SPO) for storing case and pulse attachments and If you have SPO repository, then you can configure Pega application to connect to SPO repository. All you need to do is download the SPO component from Pega exchange here (https://community1.pega.com/exchange/components/sharepoint-online-integration) and configure the same in your application. 

If you are trying to use the SPO for a different use case, you could use the data pages included in the SPO Pega exchange component or reference the connectors directly from your own data pages. Please refer to the SPO Pega exchange component install guide that is available when you download the component from Pega exchange that explains the set up needed to use the component and the list of data pages included in the component.