How can I upgrade my iPhone myself

iOS 14 has not been signed in over 2 years. If you own a compatible iPhone, which can be updated, you would only be able to update the current iOS 16.2. Which leads me to believe you likely own an iPhone 6 or older iPhone, which cannot be updated past iOS 12.5.x. If that is your situation and you need iOS 14 for an application, then you will need to invest in a newer, more modern iPhone.

jalin99 wrote:

How can I upgrade my iPhone 6 to iOS 14

You can not.

The iPhone 6 is not compatible with iOS 13, 14, 15, or 16.

The iPhone 6 can not run anything later then iOS 12.5.6

If you require a later version of iOS, you will need to purchase a newer phone.

What iPhone do you have? If your iPhone is compatible (iPhone 6S or newer), see here - Update your iPhone or iPad - Apple Support

If you encounter any issues, try the steps here - If your iPhone, iPad, or iPod touch won't update - Apple Support

Otherwise, please post back with relevant information.