i just bought iphone 15 and when i press to fo the update it just lags in the loading

If your iPhone wont update, take a look at the articles below for step-by-step guidance.

⇢ If your iPhone or iPad won't update - Apple Support

You can also update your iPhone from a computer.

Mac with macOS Catalina or later

⇢ Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

Mac with macOS Mojave or earlier, or a Windows PC

⇢ Update your iPhone, iPad, or iPod touch with iTunes - Apple Support

Force-restart, and try again.

Force restart iPhone - Apple Support

Hold the third button press past any sliders that might appear, continuing to hold that third press until the Apple logo appears.

If that’s your Wi-Fi network, restart that, too.

Papajohn1234 wrote:

I just bought it and now I’m trying to set it up and if I don’t update it it doesn’t leave me to transfer the data from my old iPhone

If your iPhone is downloading a newer iOS version, it’ll “lag” for a while performing that download, depending on your network speed. Wireless transfers can also take a while, moving data from one device to another.