Milford Sound is roughly a 2-hours drive away from Te Anau or 4-hours from Queenstown. The road surface is always sealed.

From Te Anau follow Milford Road (SH94) , one of the most scenic and 'waterfalls' road in New Zealand. Also you'll need to drive through the famous Hommer Tunnel, built in 1954. Drive up to the end of SH94 where you'll find a huge free carpark. Here, you'll require to leave your car and walk (about 10min one way) to the Information Center.

Alternatively, you may choose to travel by bus. There are lots of companies in either Te Anau or Queenstown which have these options.

When in the Information Center, you have plenty of companies/cruises you may choose from. Starting from 1.5 hours cruise and finishing with overnight ones.

You'll see Wairereata Falls on the way back, a few minutes after Stirling Falls. It is NOT a waterfall which drops to the fiord strait away, but drops into the one of multiple Fiordland rivers. Look over the mountains near the Harrison River valley, you'll admit the waterfalls from a distance (very well visible in a good day, but absolutely not seen when it's rainy).

Note: You may choose different options where you can see the waterfalls as well. It could be Milford Sound kayaking (start from Milford Sound) or Milford Sound Scenic Flight (start from Milford Sound/Te Anau/Queenstown).