u/Frequent-Editor-9420

I created some entities, but when I try to add a custom animation to them, the game either won't launch or it launches but without any textures, so the screen is black. Does anyone know how to help me, or provide links to tutorials? I'm in version 1.21.8 I think. thanks in advance. and, if possible, without a plugin. I do everything on blockbench. i'm used the version 2025.3