You don't.. you sync both the Iphone and lightning to a server, such as Google, yahoo or icloud.

The application I had before was one step.

You asked how to do it.

If you have this application use it.  No one here knows what your talking about because you don't synchronize with an application of any sort if you do it correctly.

Waltezell-

I found a solution for you.

Fewer gizmos and less complexity can produce more product for those who want to work. The people who never use a desktop look down on people like us. So I am sympathetic. I put off buying an iphone for years because I had a BB Bold that I liked and could sync without using a server. In some parts of the country, internet service is not really that great or reliable, not to mention security concerns, real or prospective. After a long search, I found a solution that actually works and it is a big improvement over my BB setup.

Other forums ask your question, but this is the first place Tbird users should look, so I am replying here.

BirdieSync is a British company that will sync Tbird contacts and calendar to the iphone contacts and calendar directly. Iphone syncs over your wifi to your desktop machine. After a 30 day trial, your registration cost is ~$30. It supports android and windows phones also via usb.

Best $s spent in the office lately. Good luck.