"How to spell" in Engpsh can be translated as "怎么拼写" in Chinese.
This phrase comes from the verb "to spell," which means to write or name the letters that form a word in correct order.
Examples:
Can you spell your last name for me?
(你能告诉我你的姓氏怎么拼写吗？)
Please spell "receive" for me.
(请告诉我"receive"怎么拼写。)