Carefully stuff the root ball of your violas (or whatever small plant you're using) into the opening in your egg. At this point, you might find that you need to take off more of the root ball.
Once you have put your plant into the egg, you may also find that you need to add more soil. The object is to have the roots surrounded by soil or eggshell, not air. If you need more soil, you can either add fresh potting soil, if you have it lying around, or use some of the soil that came off the plant.
After you have planted your egg, water it gently until water comes out the drainage hole. At this point, some of the soil may have settled so you you may need to add even more soil around the sides. You don't want to put soil on top of your plant. It's best to keep the crown of the plant - where the plant meets the soil - free from soil.