You will need to start sowing your cabbage seed in early spring in order to harvest successfully in the autumn. The best time to do this is February.
Remove from the water tray and place in a well lit area such as a windowsill or bench in a heated greenhouse. Either cover with glass or place in a propagator until the first seedlings emerge or leave uncovered and water frequently by spraying daily. Do not allow the compost to dry out (or become waterlogged). The seedlings are ready to transplant when they are showing two strong leaves.