There’s a special style set of styles you can use in a Text asset which be will be displayed to learners at different stages as they interact with a particular screen. For example, you might have set up a Hotspot Image which lets a learner click on different parts of an image to see more information about what they've clicked on, displayed in popup subscreens (see the knowledge base article “Making screens interactive using subscreens”). You can use the different instruction text styles so that the learner, first of all, sees a message saying “Please click on the picture to get more information”. Once they've clicked on the first hotspot that message changes to “Keep on clicking on other parts of the picture to find out more”. Then, once they've clicked on all the hotspots, the message changes to “Now click next to continue”.

You can achieve this quite simply by adding three Text assets into the same content block and adding your three different instructions into them:

Now assign each of them a different Instruction Text style:

For the first text which will appear when the screen is first displayed, select the Instruction text (Initial) style and click Apply:

For the second text message, select the Instruction text (Intermediate) style and click Apply.

Finally, select the Instruction text (Final) style for the third text message and click Apply.

Now when you preview this screen and start interacting with the Hotspot image you’ll see one message being replaced by another, at the same point on the screen (if you've placed them all in the same content block).

Note: Since the Instruction Text styles do more than just show text in different font styles, you should only use them when you want to achieve this kind of interactivity.  

Also note: You can only have one of each type of instruction text on any given screen. If you try to add more (for example two different text assets assigned to the "Instruction text (Initial)" style then you will get an error when you try to preview that screen.