Hi JackTowney, 
To use Nukes/Dragon make sure you have the out post upgraded to a Missile Silo/Dragon Lair and then arm the out post. This takes 24 ticks to do and if taken will be interrupted. After the 24 ticks you can launch the Dragon/Missile like a regular squad except you can only attack with it. 
Hope this helps. 
For more information please check out the BD Wiki: 
http://wiki.battledawn.com/index.php?title=Nukes