I think sfbp is referring to something else than me. The F7 is further into the process of disabling driver signature enforcement on the video. Here is Microsoft's version of how to do it:-
Go to Settings > Update & security > Recovery > Advanced startup > Restart now.
Choose Troubleshoot > Advanced options > Startup Settings > Restart > F7 or 7.
Once it restarts, you may now install any third party drivers. Note that the next time you device restarts, driver signature enforcement will be enabled again."