Try to click setted Farming/Storage zone.

Did find 'CropSettiong/Configure' Button? side of description in left-bottom.
There you can set type of Food and it golem works auto farming.

click farm zone, lay it on the floor tile just like ur storage. then click the zone to plant what u want.

i believe tree grow slower , but apple tree yield both food and wood (if u do ballista build, u might need dozon apple tree on top of ur regular food source)

Thanks guys! Couldn't figure it out either. It works now!

Keep in mind that once you select a crop and they have planted everything, you may want to UNSELECT that crop in the same way. This will ensure that they do NOT try to replant anything and will just harvest. This is important to save time since you generally only get 1 planting in on normal soil.
This does not apply to engineered/farming tiles since you can take those with you so to speak.

Keep the zone sign empty means harvest only

And delete zone mean don't harvest

delete all zone actually faster then lock all golem plant and harvest, but don't forgot to renew it