In general, what does epinephrine do, i.e. how does it work to remedy anaphylactic reaction? Thank you.

In many. ways it helps- acts on a number of receptors causes constriction, or tightening, of the blood vessels, which decreases swelling and also helps to increase blood pressure, increases the heart’s contraction and heart rate, which can help to prevent or reverse cardiovascular collapse. Epinephrine relaxes the muscles around the airways in the lun.
A potent vasoconstrictor. that what epinephrine mainly does during shock, it constricts relaxed blood vessels so blood pressure is restored, hence blood reaches vital organs (brain, heart, kidneys, liver,..) again.