Wilson was introduced as an unnamed social worker in Harlem (during the 1960s), who was recruited by the Red Skull under false pretense. The latter then used the Cosmic Cube to give Wilson psychic powers, which allowed him to communicate telepathically with birds (and thus, control them). Wilson eventually discovered the truth about who the villain and his allies were, and escaped. Shortly thereafter, he encountered Steve Rogers, who convinced Wilson to take on a superhero persona: Falcon, a crime-fighter whose strength is enhanced by his suit (which also allows him to fly).
Falcon would go on to have several adventures with Captain America in the 1970s, when Steve Englehart retconned the character’s backstory so that he’d spent some time living as a gangster called Snap, following the murder of his parents (Wilson’s memories were revealed to have been altered by Red Skull, via the Cosmic Cube). The superhero was also briefly an Avenger during the late ’70s and late ’90s, and appeared in a handful of Captain America comic storylines in the early 2000s (he’s now a recurring player in the regular CA series, which began with #6000 in 2009).
Details are being kept under wraps, with regards to what elements from Falcon’s comic history will be retained for the Captain America sequel. The screenplay by Christopher Markus and Stephen McFeely is said to take place primarily in the present-day, as Steve Rogers (Chris Evans) carries out missions for S.H.I.E.L.D. Moreover, recent rumors have suggested the film will be heavily oriented around the organization and its employees (including, Black Widow (Scarlett Johansson) and Hawkeye (Jeremy Renner)). Hence, it’s entirely possible that Sam Wilson will already be a S.H.I.E.L.D. employee, at the beginning of Captain America 2.