how to setup apple devices ( iphone & ipad ) to be able to find each other

If you own both devices, you must log in with your Apple ID on both of them and ensure that Find My is activated on both devices. It is usually activated from the start, but you can check for yourself.

Go to: Settings > Apple ID > Find. Make sure it is enabled.

Now you can open the Find app, either on your iPhone or iPad, click on devices in the bottom bar. If you're looking from your iPhone, you should be able to see your iPad, and the other way around.

You also see how to set up Find here:

Set up Find My on your iPhone, iPad, iPod touch, or Mac - Apple Support