You can take the Airport Express from Capital Airport to downtown.
Tips
culture
Full name 北京首都国际机场, IATA code PEK. Opened 1958 and long Beijing's main international gateway. Since 2019 shares traffic with 北京大兴国际机场 (Daxing, code PKX) — locals still call this one 首都机场 or just "T3" after its landmark Norman Foster terminal.
mistakes
首都 is read shǒudū (not shǒudōu). 都 is a heteronym: dū = capital, dōu = all/already. Always dū in 首都, 都市, 都城.
