Be more specific. Why wasn't it working? What do you think went wrong? I recommend you take a look at the capx again and go over it thoroughly. You might have missed something. I just implemented a dialogue pop up system very similar to this for my game. When the player collides with an important game upgrade, you get a message explaining the button to press to activate it. At first, I couldn't get it to work but I didn't have the variables and "Set Text" function correct. That link and capx is just one of many ways to create a dialogue system. Use the search function in the forums and the search function in the tutorials section to find more examples. Search for "dialogue" or "cutscenes".
If you're having problems with variables, you have to take a look at the manual, other game examples and experiment with other tutorials. This is a tutorial that really helped me understand variables a bit better and helped me move forward in making my game.
https://www.scirra.com/tutorials/158/ve ... two-states