No! The way most (nearly all) Chinese learners use it is wrong. You can use it in a sentence like Jennifer's (i.e. embedded inside another question): "Please tell me how to spell this word." / "Can you tell me how to spell this word?" But, if I'm not mistaken, you mean in a sentence like:* " How to spell crocodile?" * That sentence is never used in English. It's a direct translation of the Chinese equivalent. In China, there's an old tradition of translating Chinese sentences literally into English. You should NOT translate from Chinese word-by-word. Instead read English texts and find out what people say in the same situation.
Example:
Chinese: To go restaurant , good? (qu fan dian hao ma?)
English: Let's go to the restaurant.
Chinese: Give you the money! ( gei ni qian!)
English: Here you are.