how to add texture to block custom model?

How can i add a texture to this? After all, Extra Utilities 2 mod has textured Spikes, for example.
Is there a tutorial video for that? If not, a step by step would be nice if it is too complicated.

This model is not possible to do in Blockbench because of the triangles, and CubikStudio does not let me add a texture to that.

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