how do i get my email back on my iphone6

Pull down from the top to get the Search box and look for Mail.

If you just mean the email icon (and not the emails themselves), then see FoxFifth's answer to:

What do you do if the Mail icon is gone?

First thing you might try though, is to search for the email app to make sure you didn't just move it somewhere you can't find it:

Use Search on your iPhone, iPad, or iPod touch - Apple Support

We need more specific information about what you mean in order suggest a solution.

Mail – Setup and Troubleshooting on iPad

Mail - Troubleshoot