The first places pubescent boys usually get facial hair are above their lips and on the chin. As a pubescent boy, the hair will most likely be thin fuzz and not be like a grown man's thicker facial hair. Boys can start shaving at this point if they want to.
For many boys, shaving for the first time is a rite of passage (“a ritual, event, or experience that marks or constitutes a major milestone or change in a person's life,” https://www.merriam-webster.com/dictionary/rite%20of%20passage). Boys can ask their dad, another adult male role model in their life, or an older brother who shaves for help. Don’t ever use a rusty razor or someone else’s razor. Another person’s razor could spread bacteria. When you first start to shave, use a razor with few blades. Boys can also shave with an electric razor.