This tutorial operates under the assumption you know what a keystore and signing a APK is. If you need to figure that out, google it.
Someone wanted a tutorial on this, so I made it. Hope it helps people.
Date: November 3rd, 2016
I won't be updating this
1) Goto the top right menu and press the picture of the guy
2) Press "Create keystore"
3) Fill out the information
4) Click your project on the left hand side
5) Goto build settings
6) Select "Developer Certificate" and choose your keystore
7) Make sure signed is checked
8) Click on the build tab
9) Press the lock icon
10) Select your keystore and enter the password
Congrats, it is now signed and good to go!