In the video the example was from Olympus OM-D EM-1 MKII. In this blogpost there is more information on how you can find the settings for displaying histogram in your Olympus cameras viewfinder and LCD-screen.
You can find the LV-info settings on Custom menu D in the following Olympus bodies:
E-M1, E-M5 MKII, E-M5, E-M10, E-M10 MKII, E-M10 MKIII, E-PL8, Pen-F:
You can find the LV-info settings on in Custom menu C1 in the following Olympus bodies:
You can find the LV-info settings on in Custom menu D1 in the following Olympus bodies:
With the INFO-button on your camera you can then toggle the information you see on the lcd and the viewfinder.
If you have any questions please ask them in the comments!
The whole Using Olympus playlist: https://goo.gl/9cPqo1