How to request a local crawl?

Hi,

The following training suggests that Site Admins can request a local crawl.

http://technet.microsoft.com/en-ca/sharepoint/fp123606.aspx

All modules > SharePoint 2013 enterprise search overview > 4. Search results interface choices changes and features > Slide 16

http://download.microsoft.com/download/7/7/3/773CA2C2-579B-408C-808E-A6F561194E20/Ig15_SP_IT_M07V4_searchinterface.pptx

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How can I request a local crawl?

Thank you,