Missile-like trajectory calculation First of all I want to let you  know that I'm not a Physicist, I am a Video Game Developer. I can simulate physical and mathematical equations and can also use some built in physics. 
For example I can move an object through parametric equation of projectile
$$x = vt\cos\theta$$
$$y = vt\sin{\theta} - \frac{1}{2}gt^2$$
I can get values by increasing time, $t = 0$,$ t = 1$, . . . So these values make a good projectile.
On the other hand if I use built in Physics of Game Engine then I have to only Apply some force with a 2d or 3d vector. For example I can apply force of $\vec f = 24,15,6$ with other things in hand and I can change it like mass, gravity.
So now my question is that how can I calculate $\vec f (second method)$ or $data$ to populate in first method that the body will land on a specific predefined point.


*

*I'm repeating the objective is to launch a projectile such that it will land on a specific predefined point?

 A: One of the pieces that you need is called the range equation (assuming that you are firing from the ground):
$$
R=\frac{v^2_0\sin(2\alpha)}{g}\tag{1}
$$
So if you start with knowing $v_0,\,\alpha$, you can figure out how far it will go. But you are starting with $R$ and trying to see what pairs of $v_0,\,\alpha$ would match this, which would be quite difficult as many pairs could lead to the same $R$.
However, you say that you are applying a force for some duration, so you can use the impulse to determine the (final) velocity:
$$
\int\mathbf F\,dt=\Delta\mathbf p=m\mathbf v_{fin}-m\mathbf v_{init}
$$
Since the projectile is initially at rest, the launch velocity would be
$$
\mathbf v_{launch}=\frac{1}{m}\int\mathbf F\,dt
$$
which, if the force is constant throughout, can be simplified to
$$
\mathbf v_{launch}=\frac{1}{m}\mathbf F\Delta t\tag{2}
$$
where $\Delta t$ is the length of time the force is applied. 
So now you know the initial velocity, $v_0=\lVert\mathbf v\rVert$, and how far you want the projectile to go, $R$, so then you can solve Equation (1) to get $\alpha$.
