You're not exactly close to '77, but not far.
Go to the Civic Center BART/Muni station and jump on the outbound BART. You buy your ticket at the little ATM looking machines and the charts next to them tell you how much to pay. It shouldn't be much as you're just going to the next stop. You'll be going to the 16th Street station.
Take BART to the 16th Street station at Mission Street. '77 is on 16th, just a door or two down from Mission. Be careful on that corner/ station, as it's plagued with junkies and crack-heads.