How to install In-App Purchase from the Unity Service tab?

I imported the Unity IAP. Then within Unity (Assets>Plugins>UnityPurchasing), the folder Unity Purchasing was available. I created an IAP script to run the service but I received an error that the script was missing something. After doing some research, in this Unity Forum https://forum.unity.com/threads/purchasing-the-name-standardpurchasingmodule-does-not-exist-in-current-context.457131/ I notice I didn't install the UnityIAP and UDP within the UnityPurchasing folder.

After installing them both, at first UnityIAPby itself, didn't work, then UDP by itself, didn't work, UnityIAP and UDP together in that order, didn't work, lastly UDP and UnityIAP together in that order, lol didn't work plus all the scripts in my game also didn't work no matter how I installed the In-App Purchase packages. Sometimes download iterations of the service will constantly try to download the same thing without stopping to the point I would have to force close Unity and manually delete the UnityPurchasing folder before opening Unity again.

After deleting the UnityPurchasing folder and resetting Unity, the game scripts were working again but I was not able to use the Unity Service In-App Purchase. I'm I installing it wrong or missing a step? and Is there a scripting tutorial that worked for you in 2020?