Sometimes you're location may be tricky to find, even using a GPS. If you need to add additional directions or instructions, add them in Settings - Locations. This is also handy if you need to make notes about parking, one way streets or other nice to know information that will make it easier for your client to arrive on time for their appointment.
Select the Location and toggle "Show location to clients" to on. Enter the address and let Google find it.
Once you are happy with what Google has pinned, Scroll down to "Directions to location (optional)" and add the special directions.
Remember to save your changes.