Just put some arugula seeds on the top of the soil, cover with a layer of dry soil (1-1.5 cm) and use a spray bottle to sprinkle some warm water over it.
Cover with a piece of cling film and then put them in a warm place.
After about 3-7 days the first shoots will appear. This is when you will need to remove the cling film and transfer the plant to a more permanent place to grow.
When the leaves reach the height of 4 in (10 cm), you can start to harvest them.