"管理国家的本领" can be translated into English as "the ability to govern a country" or "the capability of state administration".
"The ability to govern a country" emphasizes the practical skill or proficiency in managing a nation's affairs.
"The capability of state administration" focuses more on the inherent capacity or potential to perform administrative functions at the national level.
Both expressions are appropriate depending on the context and the nuance you wish to convey.