Usama started his writing as a child. He made his film industry entry in 2009 through Dan Kiggundu's Maryland Productions, where he debuted as a script editor and supporting actor in the TV drama Pain of Lies, which premiered in 2011. Through the Uganda Film Network, he later joined the Mariam Ndagire Film and Performing Arts Center, where he worked on his first short film, Hello, which won the overall best film at the 2010 MNFPAC Awards. In July 2011, he made it to the final selection of the 12 screenwriters from all over East Africa to participate in the 7th Maisha Film Lab, ending up with a collaboration with Diana Karua in the making of the movie She Likes Prada. Later in 2011, Mukwaya won the Young Achievers Awards in the film and television category, the youngest among the recipients of the award in the newly introduced category alongside Rwandan President Paul Kagame, who won the lifetime achievement award. Amidst the other four young directors, he directed his first film, Smart Attempt, written by Julian Nabunya and Abel Mwesigwa, during the first season of the Movie Furnace program in August 2012. He went on to participate in the program's second season with his short film In Just Hours, emerging as the season's winner for best short film director. He has worked as a general secretary and treasurer of the Screenwriter's Guild of Uganda Film Network and as general secretary of the Pearl International Film Festival before being appointed festival programmer for the 7th, 8th, and 9th editions consecutively. In July 2014, Mukwaya started his own film production company, O Studios Entertainment, based in Uganda, that immediately opened with the production of the short film Tiktok, written and directed by himself. The studio has continued to produce various films, including his directorial debut, Love Faces.