Create a Start Point, and an End Point. After that, you need to add points in between and position them randomly based on how effective you want the lightning to look.
After that you simply just add in parts position them to each point, use a bit of math from point to point each and you can come up with this effect.
Hack Around Way:
Build lightning models (make each one different looking)
CFrame the models primarypart and use a for loop from the beginning to the end of the lightning’s streak making it fade away as it appears.