The keystone Comp. is a very powelful tool to correct the perspektive.
Again in this video the example camera was a OM-D E-M1 MKII. Here is some more info on hoq to turn on the Keystone Comp. in different Olympus cameras.
In Pen E-PL9 set the mode dial to AP and highlight the Keystone Composition and press OK. The correction is made with the Control Dial. By pressing the INFO-button you can make the horisontal adjustment.
In Pen-F, E-M10 MKII, E-M5 MKII, E-M1 and E-M1 MKII Keystone Comp. can be found from the Shooting menu 2. Use the front and rear Dials for correction. If you want to change the exposure settings while Keystone Comp is On, press INFO-button to toggle the info.
In E-M10 MKIII set the mode dial to AP and highlight the Keystone Composition and press OK. Use the front and rear Dials for correction.
Pen E-PL8, E-M5 and E-M10 does not have this feature
If you have any questions please ask them in the comments!
The whole Using Olympus playlist: https://goo.gl/9cPqo1