how do I type a letter on my MacBook Air to mail out to a state department?

Your Mac comes with three free top-notch apps (pre-installed, if memory serves):

• Pages -- This is a word processor that serves the same function as Microsoft Word.
• Numbers -- This is a spreadsheet app that serves the same function as Microsoft Excel.
• Keynote -- This is presentation software that serves the same function as Microsoft PowerPoint.

All three of the above apps will open documents created with their Microsoft counterparts.

Sounds like you'll want to use Pages. Here's the user's guide for that app: Pages User Guide for Mac - Apple Support

Hope this helps you.

See: how do I type a letter on my MacBook Air? - Apple Community