I am a college student leaving the country Jan 13 for 4 months. How do I request an extension for filing?

[Opus 17]

You can file the extension request online starting in March, you can probably file online from overseas since no payment is required for just the extension.  

Or, print and mail in a copy of form 4868.

Whichever way you request the automatic 6 month extension, you can e-file your return when you are ready, up to October 15.

Or, if you are overseas, you have an automatic 2 month extension to June 15, BUT the only way to use this extension instead of the automatic 6 month extension is to print your return and attach a statement explaining your circumstances; you can't e-file with this extension.  

https://www.irs.gov/forms-pubs/extension-of-time-to-file-your-tax-return