where I export data from a tile in a report to an Excel file.
Reports don't have tiles. They have visuals.
the actions where I can export the dashboard to a SharePoint location
Please elaborate. I am not familiar with that feature.
in a report where I have read-only access
Power BI reports are (sadly) by design read-only.
Assuming you mean a report visual - click on the visual's ellipsis (...) in the top right corner of the visual. Select Export. Summarized Data... Excel with live connection. That will give you the DAX query that was run to populate the visual.
