I don't know where to start with texture atlasing

so, i just finished publishing my vtuber model into vrchat via unity and it says that my optimization is poor. i have about 14 textures and unity suggests that i do some texture atlasing to improve the performance.

i’ve seriously watched about 4 different videos and i have no clue how to wrap my head around it.

idk if someone can give me a step-by-step or some pointers? because i am completely lost.

my model is the one i have on if that helps