i need to know how to update my iphone 6

If you are trying to upgrade to IOS 13, you can't upgrade an iPhone 6 to IOS 13. If that isn't what you mean, more information would help.

iOS 13 and iPadOS are compatible with these devices - Apple Support

Update your iOS device

Get help with over-the-air iOS updates

Update – Can’t or can’t restore

Hi Anastasiah15,

I assume you mean update the operating system, IOS. You can update your iPhone one of two ways, directly from the device itself which is the easiest or from within iTunes on your computer.

First, you should make an iCloud backup. To do this go to Settings > ICloud > ICloud Backup and tap Back Up Now. You need to be on Wifi for this to work.

To update the Operating system on your iPhone, go to Settings > General > Software Update and follow the instructions to update the software.

To do the update from your computer, connect your iPhone via the lightening cable to your computer, open iTunes if it doesn't open automatically click General or Settings and then click the Check for Updates button.

I hope this helps