To create a dilation using GeoGebra, you must have a polygon and a point already drawn. Click the down arrow on the transformation tool and select dilation. Then select the polygon and point. Enter k and voila! You can enter fractions or decimals, 0<k<1, if you want a reduction.
I uploaded to Moodle a file that already had the triangle and point for the students to download. I created a handout with instructions for an enlargement and a reduction without using those words. I asked them to compare the figures and to compare the coordinates. While I was planning our next discovery, I remembered I could use the ABC text tool to type the directions in the GeoGebra screen itself. The divider can be dragged to the left to make more room. Just click where you want to type. If you need to move the text, just click on the select arrow tool then click on the text and drag where needed.