Integrating those weapons info FPS Game Starter Kit is relatively easy, plus I already did most of the heavy lifting and prepared pre-configured weapon child classes that you can just extract and start using the weapons right away and fine-tune as you see fit.
1. Create a new FPS Game Starter Kit project and add Sci-Fi Arsenal Vol.01 to it
2. Download end extract the pre-configured weapon child classes that I made, you can put them anywhere inside the Content folder. Use Windows Explorer (or whatever your default file browser is)
NOTE: if your version isn’t listed, follow the regular how to make new weapons tutorial, as literally any skeletal mesh can be used as a gun.
3. Add them into the level
To learn more and expand it further, check out these tutorials: