To write on the sign it must be in your inventory. Then right click it and select Rename. Enter whatever shall be written on the sign. After this you can plant the sign. Just stand where you want to have it and right click, then select Plant. If the sign doesn't point in the right direction after planting, right click it, then select "Turn item clockwise" or "Turn item counterclockwise" but remember that everybody can turn a sign.
[[Category:Items]][[Category:Fine Carpentry Items]][[Category:Decorations Items]]