Beam weapons need: The weapon itself (on a turret or hull mounted), an active sensor to identify the target, a beam fire control (it's separate from missile FC) to lock on and fire at the target, and power from a power plant equal to the power requirement you designed it with. You have to design all these parts separately.
Missiles need: The launcher, an active sensor to identify a target, a fire control to lock on and guide the missiles, and a magazine of missiles to fire. As well as, obviously, the missiles loaded into the magazine. Oh, and I would recommend the ejection chance tech for magazines. If your magazine goes off your ship is in big trouble, I believe it takes 20% damage of all the warheads in the magazine - which could add up to quite a crippling blow (possibly fatal) depending on how powerful the missiles are and how many are left in the magazine when it's hit. I encountered a meson wielding ship in one system that went through my armor and got a lucky hit on one of my magazines for anti-ship missiles - even though the magazine only held 9 missiles, each had 24 point warheads - so a total of 43.2 additional internal damage from a lucky one point damage hit.
The resolution matters for the missile fire control too - if you want anti-missiles make it 0 to target them, if anti-ship you want it tuned to about the size of the ships you expect to target to get the best range.
Range of missiles will depend on your technology. Try to pair up missile range with your fire control and active sensor capabilities - active sensors need to be 3x the size to achieve the same distance as missile launchers, so that's usually the limiting factor. However, you can make a large active sensor on a scout ship to highlight targets for your other ships with fire control 1/3 the size to target.
For instance, I have active sensors size 10 on a scout for long range detection, accompanied by missile destroyers with size 3 fire controls set to the same resolution. The scout lights up the targets for the missile ships to shoot at. The ships don't have to be close to relay target information - I often keep my less well defended missile ships in the back to provide missile support while my other beam armed ships close in. The missile ships only have size 1 actives, just as an emergency fire solution if they find themselves without the scout or if the scout has its sensor knocked out.