You can launch (open) an application in any of several ways:
Single-click an icon on the Launchpad, described on the following pages.
Single-click a program’s icon on the Dock, the Sidebar, or the Finder toolbar.
Use Spotlight. Hit -space bar, type the first letters of the program’s name, and then press Return.
Double-click an app’s icon in the Finder.
If you’ve added the Applications folder to your Dock, then click the Dock icon to open the pop-up fan, grid, or list of icons. Then click the program you want (or even type the first few letters of its name and then press Return).
Select an application icon and then press -O (short for File→Open) or -.
Use the submenus of the menu’s Recent Items→Applications command.
New in macOS Sierra: Once you’ve opened the Recent Items→Applications submenu, you can hold down the key to witness a startling sight: All the program names (Preview, Photoshop, and so on) change to say “Show Preview in Finder,” “Show Photoshop in Finder,” and so on. The Recent Items command, in other words, now gives you a direct way to jump to the icon of a program you might want to open, huddling in Applications or whatever window it’s in.
Open a document icon in any of these ways, or drag a document onto the icon of a program that can open it (whether in the Dock, the Finder toolbar, the Sidebar, or a folder window).