You just have to put the tube through the net pots so that the water coming out the tubes gets onto the roots/seedling. I assume you are using rockwool cubes, so you just have to make sure those get soaked and you're good.
just put a rockwell cube or organic plug in the middle of the clay balls so the balls hold the cube/plug in place the put the seed in the cube ..... I have the top of the cube and the balls level