Prototype Rapidly: Build basic or advanced geometry, right in Unity, with zero creative barriers. Play Instantly: Playtest at any time, then edit immediately, and never leave Unity. No time (or sanity) wasted.
You can see many tutorials on official youtube channel, see this:
The install work into Asset Store tag area into your Unity 3D game engine.
You need to search with the word ProBuilder then use Download and Import buttons.
Next, You will see a window with all scripts and objects to import it ( use All and Import buttons).
After the tool is install you can see a folder into Asset area and you can use this tool from: Main menu - Tools - ProBuilder .
This tool come with default 3D primitives and many features.
