How do I get index of selected random from list?

I am trying to create a text choice adventure game that takes random scenarios from a list and provides choices that are specific to that scenario through a notifier. The message for the notifier is provided as a random from a list of scenarios however I need the index of the chosen random of that list in order to gather the corresponding text for the answer buttons. I plan to do this by getting the choices from a new list which will be chosen based on the index of the scenario. Once I figure out how to get the index of the random it would also be helpful to know if there would be any way to make an if then statement in the place of the empty button texts that basically goes as follows:
If chosen random index of scenarios list is 1, then get list choices1 index 1
Else if chosen random index of scenarios list is 2, then get list choices2 index 1
and repeat for button 2 only altering the index of the choices.

Use the Math random number block from 1 to the length of your Scenarios list. Then you have your index to select your list item

Before you go stuffing your app with text blocks, study examples of loading text from tables.