The earliest you can get this is farm level 10. Keep in mind this is the level of the FARM and not your character. You can join someone else that has an item for this already.
At level 10 you can buy a picnic table and once its placed you can sit at it with
and the achievement unlocks. The table can be found in the decorations tab and costs diamonds. This will count towards your 1,000 decoration achievement as well.