The help menu is kind of messy for first-time level makers. Articles found in the above link are pretty complicated lol. Thus let's keep it simple.. Go to Tools -> Level Properties and double click on one of the empty text lines in the box below. Now, right click on the the place in your level where you want the text to appear, and click Select Event. There, click Gameplay -> Triggers & Scenery -> Text. Now set the number of TextID to the number of the previously written text line. The rest explains itself I hope.