how do you ride them?

make sure you subscribed to the entities library mod
when you load a world enable developer options and press F2 twice, it will say [Mod] turtles.amphithere loaded and it will also say turtles.entity loaded with no errors. if it says that then it's working, type /disableachievements and "/summon amphithere 1 blue"
if you're asking about using the wand put the approval & food in your inventory, place a wand next to a dragon, and stand next to the wand

Could you make some sort of instruction guide for this please, I'm probably just being dumb but I can't figure out how to get this to work

amazing

Thanks! that's bc the code is pretty restrictive, it wouldn't be possible to provide custom code for the zombie npc outside of its events. instead I started from scratch and put it into the entities library mod. the mod could be used to make a boss zombie but it would be hard since it doesn't inherit from npcs; it's actually a scripted block thus the modder would need to provide all the zombie stuff

Wow this is impressive I never even knew you could implement custom NPC's into Colony Survival, surprised that nobody has used this feature to code proper boss zombies yet.