How do I update my iPhone

This explains how to update your phone.

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

You may have other issues that are causing your battery problems. You may need to have the phone looked at by Apple or an authorized service center.

Thanks for reaching out, Philipstephen.

It looks like you're asking about updating your iPhone, as well as having some issues with its battery. We can help.

For hardware issues, such as those with a battery, you can Contact Apple for support and service.

If you need help with updating, you can check out Update your iPhone, iPad, or iPod touch.

Hope that helps.