how do i switch graphics mode on 2016 new Macbook

The memory allocation to the Intel HD Graphics 5300 processor in that model appears to automatically

be allocated up to 1.5GB from system memory in the MacBook (Retina, 12-inch, Early 2015) model.

https://www.apple.com/macbook/specs/

You've asked a question in a version MacBook that usually has no ability nor dual-GPU.

If you have a new MacBook Pro 15-inch model please identify the model & specification.

There does not appear to be a 'secondary graphic processor' in 12-inch Retina MacBook as some MacBook Pro 15-inch models.

• About integrated video on Intel-based Macs - Apple Support

Perhaps someone else can shed more light on this topic, if you need to enhance the display output

or other aspects of using the new model MacBook Retina 12-inch 2015. And the adapters are limited.

The 2016 models don't appear to be in the Apple store. -- Regarding the 15-inch MacBook Pro, see:

MacBook Pro (Retina, 15-inch, Mid 2015) - Technical Specifications

Good luck & happy computing! 🙂

You need to identify your Mac model.

There is no such thing as a 2016 MacBook. The latest MacBook is the 12" Retina MacBook Early 2015 model. And you have posted your question in the forum area for the 12" Retina MacBook.

Note: There are no 2016 MacBook Airs or MacBook Pros either.