By default Ninject will allow you to auto resolve concrete types with the correct bindings. In you instance you could just do:
public void Main()
{
Target sometarget = new Target();
IKernel kernel = new StandardKernel(new Bindings());
//var weapon = kernel.Get<IWeapon>();
var character = kernel.Get<Character>();
character.Attack(sometarget);
}
For more information read through the Ninject wiki: https://github.com/ninject/ninject/wiki/Dependency-Injection-With-Ninject