Is there a pot of some description?
Put the dry disc into a bowl, and let the kids add some water. It should absorb the water and expand to make compost.
Once all absorbed [you may have to add more until it is fully expanded] put it into the pot. the cat nibble might be fertiliser so mix that in before putting into the pot.
Open the foil packet carefully, and sprinkle over the top of the soil.
Get a kitchen fork, and gently move it across the top of the soil as if you were putting very small fork lines onto the top of a shepherd's pie.
Place the pot into a tray of water, and let the soil soak up as much water as it can - you should see the surface of the soil start to get wet.
Then tip the excess water out of the tray [lift the pot out when you do this], and place it back on the tray to drain.
Then wait a year or two to get a strawberry to fruit properly - so go out and buy some strawberry plants in the meantime!