How can a voltage follower's output have any current through it?
The output current is provided by the voltage source, which is connected to the pins 4 and 7 of the op. amp.
Ignoring the negligible input currents, these are the relevant ones:

Notice that B1 provides current to the potentiometer RV1, which acts like a voltage divider, and B2 provides power to the op. amp. (and its output load).
As noted, this is a real op. amp., so there is negligible currents at the inputs. There are also other non-ideal characteristics, like, e. g., the model in your post is not a rail-to-rail component, so the inputs and the output do not work using the full power source voltage range.