I am having trouble adding multiple materials onto my Houdini model in Unity. Every time I import it into Unity only one material goes over the entire thing. How would you get materials onto different parts of the model?

You'll have to create primitive groups, then assign a material for each group. In Unity, you might have to turn off Split Geos by Group under the Cooking tab on the asset's Inspector UI.

See this video that shows setting multiple materials via primitive groups:
https://youtu.be/zzcBhuRLJZo?t=109 [youtu.be]

Thank you, that worked!