What to do when planted field? (Farming Simulator 17)

The first day of play, do not throw a dirty sponge, RV.
So. I gathered together the available harvest in the first field and the tiller handled the second (after the harvest on the ground and processed it), filled with fertilizers, washed all the machines and tools so... What to do next? Long it will grow? If long, WHAT to DO WHILE IT's GROWING? (About three times to fertilize I know, but, apparently, these three times (for two) will last five years.
So while I helped the neighbor farmer to harvest and now I will fertilize the field, but this is the lesson? Stupid to help themselves and others?
Maybe more animals to breed and to fell the forest, till the growing crop and rotate all of this?