How to use a semicolon...
To join two closely related independent clauses without using a conjunction.
There were five siblings; they each have red hair. vs There were five siblings and they each have red hair.
When writing a list that has internal punctuation.
We visited Detroit, Michigan; Cincinati, OH; and Chicago, IL. vs. We visited Detroit, Cincinati, and Chicago.
Before a conjunctive adverb when joining two independent clauses.
Sarah was lost; however, she kept trying to find her way home.