How do I fix the cs0234 error for probuilder api

Hi I wanted to test out the probuilder API for my current project and I've ran into a problem I just can't figure out how to fix.

I have installed Probuilder through the packet manager in the unity editor and as I wanted to add the library to my script using the "using UnityEngine.ProBuilder;" command I got the error that Probuilder isn't available in the UnityEngine namespace.

The error: The type or namespace name "ProBuilder" is not present in the namespace "UnityEngine". (Possibly an assembly reference is missing.) [Assembly-CSharp].

Thanks in advance.