The most efficient way to request a license is to go directly to the page of the song you're looking for, for example Can't Help Falling in Love by Kina Grannis, and choose Request a synchronization license:
This guarantees a fast processing and avoids your request ending up in the spam folder.
You can also e-mail us at info@secondhandsongs.com, but your request might slip through the cracks as it will drown in the many emails we get every day on diverse topics.