This achievement occurs during Episode 1 - It's About Time
Once you've moved to the back alley with the Delorean after being in Edna's apartment do the following:
• Dialog (George): Any
• Interact with Time Circuit Switch.
• Interact with Time Circuit Keypad.
Marty will then travel back in time and the achievement will pop once the next area loads.
Credit to T_l_M_B_0 of PST