Locate the PPT file in Finder
Double-click the file to open it in the default app
If it does not open, right-click the file and choose Open With
Select Microsoft PowerPoint, Keynote, or another compatible app
If needed, open PowerPoint or Keynote first
Go to File
Choose Open
Select the PPT file
Click Open
If the file is in PowerPoint format and you do not have PowerPoint installed, install Microsoft PowerPoint from the App Store or Microsoft website
If the file is not supported, convert it to a compatible format before opening