If possible have a look at your tray every day

If the compost looks and dry then give a little water to each module but if it is moist (damp) then leave and check again the next day

When the seeds start to grow and you can see the stems then turn the tray around every few days

You put 3 tomato seeds into each module, once they have grown you need to reduce this to just one tomato plant per module

You do this by taking out the weaker seedlings and leaving the strongest one in the module

The strongest tomato seedling will have a thicker stem and may be taller than the rest

You should be left with only one tomato plant per module

The seedlings which were removed can be put into a compost bin if you have one