[Fyron]

You have to have 11 Starbases to build a RW, and 21 to build a SW. On one Starbase, there needs to be the Ringworld Generator (or Sphereworld Generator). A RW requires 5 Gravity Plating and 5 Hyper Density Cable components in the same sector as the Generator (and a SW requires 10 of each). These comps only fit on Starbases. So, once you get all of them built in the same sector as a star, select the Starbase with the Generator, and then do Stellar Manipulation. You'll have an option to Build RW or Build SW.