Set Session value form url parameter on page load

I am getting extremely frustrated with what what was once simple tasks in Dreamweaver and dare I say web assist plugins, to now being really confusing with Wappler.
For this instance all i am trying to do is create a session value from a url parameter on page load.
Please can someone clarify how to do this. There doesn’t appear to be a tutorial that clearly explains this. plus most of the tutorials I have seen aren’t even up to date with the current version of wappler.

Thanks in advance!