The current one way transmission times are 20 hours and 5 minutes to Voyager 1 and 16 hours and 38 minutes to Voyager 2: https://voyager.jpl.nasa.gov/mission/status/

The probes use a star tracker to determine their orientation (they apparently look for the sun and one other star). I assume they keep track of their expected position in the solar system, and this is fine-tuned with updates from the ground station. If you have position and orientation, you can compute where the Earth should be at the current time and point the antenna in that direction.