The quickest and easiest way to lower your ping is to switch from a wireless connection to a wired one. However, this may not be practical for everyone. Here are a few things that can help you reduce ping and get smoother gameplay on Fortnite:
Make sure you’re not downloading anything or torrenting in the background
Reduce your distance to the router
If you’re using a VPN, connect to a server that’s closer to your actual location
Try using port forwarding