[Fixed] The type or namespace name 'Demo' does not exist in the namespace

[IngoLingo]

This is my Error:
Assets\Opsive\UltimateCharacterController\Add-Ons\Climbing\Demo\Scripts\MovingLadder.cs(13,46): error CS0234: The type or namespace name 'Demo' does not exist in the namespace 'Opsive.UltimateCharacterController' (are you missing an assembly reference?)

Context:
I just installed Third Person Controller and then I installed the Agility, Climbing, and Swimming add-ons on a clean URP project. Now I am getting the above error. I have never encountered this error before when I used these assets with older projects.

Unity Version: 2022.3.3f1 (I would prefer not to upgrade)

FIX:
For anyone else getting an error regarding namespaces, follow this Importing guide first.

Importing - Opsive

Import Errors If you receive any errors upon import it is likely because of a namespace conflict. Lets say that you have an existing project . . .

opsive.com

My issue was resolved after following Justin's suggestion below.

 

[Justin]

Make sure you've first imported the sample scene:

Importing - Opsive

Import Errors If you receive any errors upon import it is likely because of a namespace conflict. Lets say that you have an existing project . . .

opsive.com

 

[IngoLingo]

Make sure you've first imported the sample scene:

Importing - Opsive

Import Errors If you receive any errors upon import it is likely because of a namespace conflict. Lets say that you have an existing project . . .

opsive.com

Thank you. I feel silly for not trying that before making a post.