Far is signed a bit like ahead, so be careful not to get the two confused.
To sign far, begin by making fists with both hands and bringing them together, fist to fist, with thumbs sticking up. Then keep your non-dominant fist in place as your dominant fist moves far ahead about 2-3 feet away. For added effect, squint as you sign far, to emphasize to your child that the object or person that is away is difficult to see.
Teach your child the far sign in the context of real-life activities: neighborhood walks, road trips, social gatherings, or holidays.
Teach your toddler this sign in conjunction with its contrast sign, near, and other prepositions or adjectives that show relative distance and direction.