OS X El Capitan: Drag and drop items
You can drag and drop to do just about anything on your Mac: move files and folders to new locations, add a photo to an email, or move a chunk of text in a document. You can also drag items to the Dock or the Finder sidebar so you can get to them easily.
To drag an item, select it, then hold down the mouse or trackpad button while you drag it to a new location. Release the button to drop the item into place.
Here are some examples of what you can do by dragging and dropping:
Move an item: Drag it, then drop it where you want it.
To copy the item instead of moving it, hold down the Option key while you drag and drop.
Add an item to the Dock: Drag it to the Dock.
Place apps to the left of the separator line, and files and folders to the right. If you moved the Dock to the side of the screen, place apps above the line, and files and folders below.
When you drag an item to the Dock, an alias is placed there.
Remove an item from the Dock: Just drag it out until you see Remove. Only the alias is removed from the Dock. The actual item isn’t removed from your Mac.
Add an item to the Finder Favorites section: Drag the file or folder to the Favorites section of the Finder sidebar. To add an app, hold down the Command key while you drag.
When you drag an item to the Finder sidebar, an alias is placed there.
Remove items you added to the Finder sidebar: Drag the item out until you see a gray remove sign (x). Only the alias is removed. The actual item isn’t removed from your Mac.
Move text or graphics in a document or email: Select the text or pictures you want to move, then drag the selected item(s) to the new location.
You can also use drag and drop with Mission Control to move items between windows and spaces. For more information, see See open windows and spaces in Mission Control.