Well smeg. I will start preparations. BTW, how do i make STOs? I reckon i will need like 400 of those.
First you need a naval space weapon, like a gauss cannon (planetary PD) or laser/railgun/particle beam etc.
Then you design a static weapon with an STO component, my recommendation is not to armor it unless you want a single gun to take decades to build. Fortification is armor for STOs.
When you select the STO component you'll be able to pick from a list of compatible weapons you've already designed, gauss weapons can be designated as PD weapons (but you might need to use a turret STO in order to benefit from improved tracking), every STO weapon can also choose to mount ECCM if available.