Choose Apple menu > System Preferences, then click Spotlight.
Click the Privacy tab.
Drag the disk or folder that you want to index again to the list of locations that Spotlight is prevented from searching. Or click the add button (+) and select the disk or folder to add.
You can add an item to the Privacy tab only if you have ownership permissions for that item. To learn about permissions, choose Help from the Finder menu bar, then search for “permissions.”
From the same list of locations, select the disk or folder that you just added. Then click the remove button (–) to remove it from the list.
Quit System Preferences. Spotlight will reindex the contents of the disk or folder. This can take some time, depending on the amount of information being indexed.