How do I make sure my phone is updated for security purposes.

Settings > General > Software Update

See ➡️ Update your iPhone, iPad, or iPod touch - Apple Support

If you don't get iOS 14.8 (current), but are told iOS 12 or some earlier version is up to date, your iPhone is too old and with hardware insufficient for current iOS versions. Your choices there are a newer (used, refurb) or new iPhone. (There are no hardware upgrades.)

This is a forum. It takes us a little time to find your question, and to compose an answer. Some of us can type faster than others, too.

If you have automatic updates turned on, yes, it did it automatically. You are updated appropriately, so you're good.

What model iPhone and what is the current iOS version on your phone? Please be patient. This is a user to user only forum. We are all volunteers helping other users here.

Check at: Settings - General - About - Version = ???

You've very welcome.