Arrival
Evidence for the migration of farming communities into Ireland comes from Cashelkeelty in County Kerry.   It is from this location that we get out dates of 3900-3000.  When the settlers came over the Irish Sea, it is theorised that they brought their animals with them on rafts led by skin boats.  

Settling Down

The way these, and many, neolithic farmers cleared lands for farms was by burning or chopping down trees with stone axes.  There were no natural cereal crops but the settlers brought with them wheat and barley. (Cereal crops, by definition, are grown for their edible seeds/grain like wheat, oats, maize, etc.)   The wheat was an early type and it had to be roasted to get the grain from it.

The fields were most likely surrounded by forests, prickly bushes with edible berries and eventually ther prickly bushes.  Some examples included wild roses, hawthorn, honeysuckle and ivy.  The prickly bushes were, in part, to keep animals away from the crops.

Domesticated sheep, goats and cattle were not native to Ireland either; they were brought by the same settlers.

Evidence from Ceide Fields in County Mayo shows how the Neolithic Irish lived.  Much like their Mesolithic (Middle Stone Age) ancestors, there were a cluster of houses surrounding a communal, multi-purpose house.  The houses were rectangular, had large tree trunks sunk into the ground and/or mud covered interwoven branches for walls.  The roofs would most likely have had holes in them since evidence shows that these Neolithic farmers cooked indoors thus needed a way for smoke to be released from the house.

Now how can we know all of this?  Archaeological evidence gives us these answers from clues like holes in the ground and stone walls.  For agricultural evidence, scientists look at the pollen counts and other
remnants in the lower levels of soil.  Below is a picture of a reconstructed Neolithic Irish house: