My phone is updated to iOS 12.4.3 but I cannont get my new apple watch 5 to pair and sync with my iphone. What am I not doing right?

The iPhone 6 will not work with the Apple Watch Series 5

Apple has a 14 day return period. Suggest you return the Series 5.

In the future when you get a newer iPhone, you can purchase an Apple Watch.

First update your iPhone (today Apple released IOS 13.2.3)then update your Watch. You might have to unpair them first. Oops! I didn't notice you had an iPhone 6.