Teeth and eyes trouble. Please help!

About a week ago I began working on a monster for a videogame project that my friends and I are working on. I’m completely new to blender and have only been doing it for something like two weeks. I’m stuck at this part in a tutorial I’m following where the guy adds teeth and eyes to the model after baking and things (https://www.youtube.com/watch?v=sPKWR7Lcs3w&t=2330s at about 51:37) . He unfortunately doesn’t show the shortcuts he’s using and I can’t tell if he’s doing a mirror modifier on the eye to just magically make it show up in the other eye socket as well or if he’s merging it with the mesh. And then same problem with the teeth. I’m not sure how he’s getting the teeth onto the mesh, or if they’re entirely separate. When I try Ctrl+J it completely messes it up as it applies the mods from one to the other. Any help is extremely appreciated!!

Here’s a pic of my project: https://imgur.com/gCPZr2e

Wrong section. This belongs in the Modeling section: https://blenderartists.org/c/support/modeling

He joined the objects, the eyes and and the teeth are joined to the main objects so they get duplicated to the other side since he has the mirror modifier active on his main object. The active object will always be the last selected object by default.

I apologize, I’m new to the website. Just a quick question with that; when I try joining the objects (the teeth and eyes to the main object using Ctrl+J), it applies my other modifiers (subsurf and displace) onto the teeth and eyes, which messes them up royally. Is there another way they can be joined that doesn’t do that?

The subdivision surface modifier should round out the eye and teeth so it shouldn’t cause any problems for such basic shapes. The displacement modifier also shouldn’t cause issues if the mesh was baked correctly, you can always just move their UV’s to a blank zone in the UV editor to exclude them from the displacement.