You will want to set variables in the (+) and (x). So, for example,
-OnSelect of (+) = UpdateContext({varShow: true})
-OnSelect of (x) =
UpdateContext({varShow: false})
Then, set the visibility of your text boxes. For text box 1, Visibility - varShow,
Text box 2 = !varShow
As you learn more, you may want to experiment with using only one button and one text box to achieve the same goal.