Note that: During the indexing stage, you won't be able to use Spotlight search.
- From the Apple menu got to System Preferences > Spotlight > Privacy tab.
- Select the desired directory or volume and add it to the Spotlight list, by selecting it and clicking on the + button.
- Click OK.
- Now remove the directory or volume you have just added to the list by selecting it and clicking on the - button.
- Close the Spotlight preferences.
- Spotlight will automatically re-index the contents of the directory or volume.