You can share your 4K video right from the standard iOS Share sheet. Once you're done, you can save it back to your Photos library or share it using any service that supports 4K video.
Whether you're starting a new project or continuing an existing one, simply import your 4K video the way you would any other video and edit away. How I shot and edited my iPhone 6s review on the iPhone 6s Plus - in 4K! You can also edit 4K videos the same way you edit other videos-using Apple's iMovie app, which lets you add themes, titles, and transitions.
AMOUNT OF 4K VIDEOS ON YOUTUBE HOW TO
How to turn on 4K video and change its shooting format