Here are some examples of how to use "afterward" at the beginning of a sentence:
Example 1:
* "Afterward, we went to the movies."
Example 2:
* "Afterward, I realized I had left my keys at home."
Example 3:
* "Afterward, the party was still going strong."
Here are some alternatives to using "afterward" at the beginning of a sentence, which might sound more formal:
* "Later, we went to the movies."
* "Subsequently, I realized I had left my keys at home."
* "Following the event, the party was still going strong."
Ultimately, the best way to use "afterward" depends on the context and tone of your writing.