The main airport in San Francisco in San Francisco International. SFO is about 12 miles from the Hilton Financial District. You can then take the BART (or a taxi) to the hotel:

Ground transportation and directions to the hotel (from SFO)
The Hilton has these suggestions.

Bay Area Rapid Transport (BART) system
We encourage you to use the BART, San Francisco's public transport system, to travel between SFO and the Hilton. It's the cheapest (approx $8) and greenest option.

• from SFO, take the air-train to the BART Station (5 mins). Go downstairs to the platform and take the yellow line to the Montgomery Street Station (30-minute ride). It's a 15-minute walk to the Hilton Hotel (750 Kearny St, on your right, you can't see it from the road so keep walking - it's there!)
  • Montgomery Street station map (you don't need to make all the little turns the map suggests: just walk down Sutter and turn right onto Kearny St)
  • BART schedule planner