Welcome....
(a fifth is smaller than a handle - I forget the oz but it's big enough)
The first step is indeed the one you might not want to do - I sure didn't- quit. Full stop. I went cold turkey from a "bigger habit" than you did (the above referenced handle, about every day and a half). Not giving medical advice since we cannot do that here, and of course it is safer and easier to even just go to the ER - with that in your bloodstream my thought is they'd help you. Detox would be assisted with meds and potassium replensihing and the like, for a couple days probably.
Besides the quitting, we need to start a recovery program. My guess is that you haven't done that second part in the past, with full commitment.
Lots of suggestions on that here- mine was (finally) AA. Others can tell you about their foundations.