Weapon firing and weapon selection mechanism for C# game

Some tips.

Represent each cannon muzzle as an empty gameobject pointing in the direction the cannonball would fly. Create a simple gameobject with a cannonball mesh (sphere), give it a rigidbody, and make a prefab out of it. When a cannon should fire, instantiate a copy of that prefab and use RigidBody.AddForce to make it fly forward in a nice arc. Use the Unity User Manual and Scripting API for further information on the required functions and variables. If you also want a muzzle flash, give the muzzle object a meshrenderer or particlesystem with the appropriate graphics. Use a Coroutine in for tformer case to enable the MeshRenderer for a fraction of a second to simulate the flash. If using a ParticleSystem, use ParticleSystem.Emit to emit a number of particles. The cannonball itself can also be given a TrailRenderer or ParticleSystem for a trail or smoke effect.

To be honest, you will struggle to get anywhere unless you start learning to code. The Unity team have done a great job of making this as easy as possible. http://unity3d.com/learn/tutorials

They key is to realise that like most things, you'll need to start simple and build your knowledge and experience over time. If you don't understand something, work your way backwards to the simplest aspect you do understand and start tackling it from that point forward.