I am confused, how to install and used radish-tools
The posted articles provide information on how to accomplish the tasks defined in the trials. The first trial is just about installation and testing out the installation by getting the published example quest to be "rebuild from the source definitions".
I suggest trying out trails in the proposed order as the challenges are increasing. But it will give a hands-on overview of the most important topics.
I know there is someone working on a more detailed howto install guide. I don't know when it will be ready or how detailed it will be - I just know the person is putting quite some effort into it.
if i want to use w2quest.exe, how do i get to access the array?
I don't know what you mean. But if you refer to changing vanilla quests that is not supported. Only the creation of new content. And to accomplish this use the trials as documentation (to build up the required knowledge).