1. Select the tag icon and you can find the custom properties from your Salesforce or Hubspot account.

2. Select any of the "Events" page from the left menubar.

3. You can find the Hubsport/ Salesforce properties with every calendar event.

4. Choose the account property at first.

5. If the account contains any opportunity, then you would need to select an opportunity property. After selecting an opportunity, the relevant stage property should be automatically selected.

Similarly, you can apply Salesforce or Hubspot properties to other events as well.