to want (something)를 is the object particle, and 원할 is the future attributive form of 원하다 (“to want”). Together, 를 원할 usually appears within a larger expression such as 무엇을 원할 때 (“when [someone] wants something”).
KO: 무엇을 원할 때 언제든지 말씀하세요.
EN: Please let me know whenever you want something.