Greetings Admin_10,
We can see you've been using Set up iCloud on your iPhone, iPad, or iPod touch and have questions on how to access Find My on your iPhones.
The instructions in this guide will help: Set up Find My on your iPhone, iPad, iPod touch, or Mac On your iPhone, you'd want to go to Settings > select your name > Find My. This way you know you're signed in and can turn on Find My. You'd also check the "Learn more" section for more links or suggestions.
You've mentioned using 4 iPhones, if they're all using the same Apple ID, this will be easy. If there are different people using different Apple ID's, check this out: Share your location with your family This might be a good solution for you.
We're hoping this helps!