Dear CJ_MD20036
Good day! Thank you for posting to Microsoft Community. We are happy to assist you.
Based on your description, we understand that you want to know how to find Outlook Web Access and Exchange Web Service URL for the calendar of conference room resource. If you have full access permission, you can open Outlook Web Access for resource mailbox by typing https://outlook.office365.com in browser -->Add your credentials (Username and Password) --> Go to your account manager --> choose to open another mailbox-->Add conference room as another mailbox -->click Open
For the URL of exchange web service for the mailbox, have search at our side and found the URL should be https://outlook.office365.com/EWS/Exchange.asmx , you can check with this.
Note: If you are not able to access the link of resources mailbox, you may need to contact your admin.
Looking forward to your response.
Stay safe and healthy!
Sincerely,
Inema Elyse | Microsoft Community Moderator