I suggest taking a look at the training videos/exercises on the Mendix Academy page: https://gettingstarted.mendixcloud.com/. It'll take some time going through them, but in the end it will save a lot of time and frustrations.
I'm suggesting these since your question is regarding very basic functionality: connecting a page (or microflow that will open a page/popup) as an on-click action for an element or to be shown/triggered when selecting a button is very simple:
I can think two ways to do this.
1 – As Wieke said before, you can open a new page. This page can have a popup layout, and you will have what you want.
2- You can use a dataview of type “Listen to Widget” configured to listen to this task list. Inside this dataview, you can retrieve the list of that selected task;
Hope it helps.