iPhone 8+I want to update software to iOS 16.7 how do I do that?

Yes, you can, but you've skipped a couple years worth of updates, so you will need to connect your iPhone to your computer and do the update using iTunes (Windows) or Finder (Mac).

This link will tell you how to do that --> Update your iPhone, iPad, or iPod touch with iTunes - Apple Support

I found this helpful Apple Support page that confirms the iPhone 8+ supports iOS 16.7 and no further:

Apple security releases – Apple Support (UK)

RegN1983 wrote:

can I update my software to IOS 15 with an iPhone 8+?

No. You can ONLY update to the most current version iOS you phone supports.

iOS 16.7. And if you update your iPhone 8+ that's the only version you can install.

Yes I want to update my iPhone 8plus

Yes I want y to o update it

The answer has already been given by lobsterghost1. Go back and read through this post.