Here's what's going on here.
In the video, Tyler says that
the oxygen and hydrogen pair can steal an electron from somewhere else
That basically means that in order to have a hydroxide anion,
In other words, the hydroxide anion is formed when the oxygen and hydrogen pair take an electron from elsewhere, usually from a metal atom.
A classic example would be sodium hydroxide,
When this oxygen and hydrogen group reacts with a sodium atom,
Another example to consider here is the auto-ionization of water, which produces hydronium cations,
#2"H"_ 2"O"_ ((l)) rightleftharpoons "H"_ 3"O"_ ((aq))^(+) + "OH"_ ((aq))^(-)#
Here one water molecule picks up a proton,
Long story short, the oxygen and hydrogen group that forms the hydroxide anion picks up an electron from another atom.