Take a look at the sentence again:
Hunched over the keyboard for hours, Charlie
used two fingers to hunt and peck out the 2,000-word research paper when
lightning caused his computer to crash, Charlie wept more tears than the
thunderclouds spilled rain.
Hunched over the keyboard for hours is a past participle phrase. A past participle phrase will often begin with an ed word like hunched. Charlie used two fingers ... is a main clause. An introductory participle phrase requires a comma when you connect it to a main clause that follows.
Go back to the sentence to try again.