Step 1 is offered several times per week at any prometric testing center. You should aim to sign up ideally at least 2 months in advance, but in a pinch you can get a spot in a couple of weeks.
A lot of people recommend Zanki, but it takes a lot of work (at least an hour per day) and if you skip days, your reviews pile up and you get stuck, so if you're not the type of person who can commit 1-2 hours per day to doing flashcards, then this might not be the right thing for you. I didn't use it at all.
The most commonly used resources are UWorld (essentially required), First Aid (also basically required), Pathoma, and Sketchy Micro. I honestly think that a year out is too long to really take advantage of Step 1 specific studying, but you can definitely reinforce material that is both important and board testable by watching the pathoma videos during the correlated block in school and following along with the manual and perhaps annotating first aid. Some people do one pass of UWorld during second year (I did not). I would recommend going through the bacterial portion of Sketchy Micro during your microbio/ID block and then again during or right before dedicated as it's incredibly helpful (the virus/fungi/parasites... not so much imo).
Relax, it'll be fine!
