"说明基本政策" can be translated into English as "explain the basic policies" or "elucidate the fundamental policies".
"Explain" is a common and straightforward verb meaning to make something clear or understandable.
"Elucidate" is a more formal and sophisticated verb, also meaning to clarify or make something clear, often used in academic or official contexts.
Both expressions are appropriate, depending on the context and the level of formality required.