EVA Mk1 Crew Hatch kerbals?

[Grande1900]

When I hover over the "EVA" button, it says "Automatic EVA Disabled, Activate a hatch." What do I do, and what the heck is a hatch?

Nevermind, Figured it out myself.

 

also if you have this problem too, just find the hatch on the end of a cabin and click on it, It will allow you to EVA a kerbal.

[PTNLemay]

Is this modded KSP or vanilla?  I always initiate an EVA using the interface near the portraits of the kerbals (lower right).