1st Single from "Planet Earth" - Get it now!

Source

"Guitar" is available for free on Verizon Wireless, all you have to do is access this Verizon page.

There you will have the option to download the song and/or get the ringtone of "Guitar".

In addition, I've also taken the below passage directly from 3121.com for a more detailed set of instructions.

To get the exclusive track of “Guitar” from Prince, download the V CAST Song ID application for free on V CAST Music-enabled phones, then go to Verizon Wireless’ music site, www.verizonwireless.com/music. Once there, play the interactive video online, hold your phone to your computer speaker and V CAST Song ID will identify the song. Customers can then select the “Get Song” option on their phones to download “Guitar” for free. Verizon Wireless V CAST customers also have the option to purchase the “Guitar” Ringtone or Ringback tone.

Step 1: Download V CAST Song ID for free to your Verizon Wireless phone

Step 2: Visit www.verizonwireless.com/music or licensed sites such as YouTube (www.youtube.com), Revver (www.revver.com), Veoh (www.veoh.com) and MySpace (www.myspace.com)

Step 3: Start V CAST Song ID on your phone, select “ID New Song” and then play the interactive video from the hot new Prince single, “Guitar” online with your phone close to the PC speaker to ID it.

Step 4: Your phone will now give you information about the song, as well as an option to download it immediately, over-the-air, for free (source)