How do you hyphenate the word stepchild?

You do not generally hyphenate the Word stepchild, because it is not a hyphenated Word. If the question is where to hyphenate stepchild if you have to break it across two lines, it is not difficult to determine this, because the two syllables are actually separate Words: step and child. If you have to hyphenate the Word to break it, you would put step- on one line and child on the next. If the Word is all on one line, you do not hyphenate it.