You can answer this question in a few ways:
Formal:
* Se llama [name]. (He is called [name].)
* Su nombre es [name]. (His name is [name].)
Informal:
* Él se llama [name]. (He is called [name].)
* Se llama [name]. (His name is [name].)
Example:
* Question: Como se llama él?
* Answer: Se llama Juan. (He is called Juan.)
Remember to replace "[name]" with the actual name of the person being referred to.