How to use Sponge with a FTB Infinity Lite Server?

I’d like to add plugins like permissions and a worldeditor.

The Sponge Docs is always a good place to start - you want the details on installing SpongeForge. You can just drop plugins (including SpongeForge) into the mods folder. There is WorldEdit for Sponge, and several permissions plugins - PermissionsEx 2.0, LuckPerms, PermissionManager come to mind, and there are a few more. Make sure you get the right builds for the version of SpongeAPI (and Minecraft) you are running.

You are amazing thank you so much.