In the dialog, click a location in the sidebar on the left, or click the pop-up menu at the top of the dialog, then choose the location where the presentation is saved. Open a presentation stored somewhere other than your Mac (such as iCloud Drive): In Keynote, choose File > Open (from the File menu at the top of your screen). Keynote shows up to the last ten presentations you opened.
Open a presentation you recently worked on: In Keynote, choose File > Open Recent (from the File menu at the top of your screen). For a PowerPoint presentation, drag it to the Keynote icon (double-clicking the file opens PowerPoint if you have that app). Open a presentation on your Mac: For a Keynote presentation, double-click the presentation name or thumbnail, or drag it to the Keynote icon in the Dock or the Applications folder.