When you export to Excel, you're creating a separate document, a spreadsheet that isn't part of Power BI. Any changes that you make in the Excel file won't impact the data in Power BI.
Select the visual in the report.
Select More options (...) from the upper right corner of the visualization. Choose Export data.
You'll see options to export Summarized data or Underlying data. Select the Summarized data option if you want to export data for what you currently see in the visual.
What happens next depends on which browser you are using. You might be prompted to save the file or you might see a link to the exported file at the bottom of the browser.
