Can someone point me in the right direction on how I can replicate this model/character?

I want to be able to make character models just like this. I think it’s amazing. I have no idea where to start.
I don’t want to actually create my own characters, just either purchase some character rigs or use free ones. But I have no idea how I would go about converting them into ROBLOX.

This model I think is made by ROBLOX Drooling Zombie (Rthro) - Roblox . Is there some sort of template I can use? Any information is greatly appreciated. Thanks.

Does this help? NPC Kit | Roblox Creator Documentation