So the first aid here are the links below
First Aid for the USMLE Step 1 2014
First Aid for the USMLE Step 1 2013
First Aid for the USMLE Step 1 2011
I purposely didn't put the 2012 edition because it has way too many mistakes, and its not worth your time to spend 2 days fixing the mistakes in the book that you already paid so much money for, and i recommend 2013 or up since they are in color which really helps.
First Aid only helps if you already know the material and now you are just revising things and memorizing what you dont know so please remember that and the most important thing doing as many questions as possible and this is a must just do as many questions as you can and i like, almost everyone else recommend usmle world for that.
Make sure there is alot of revision, and to focus on the topics that you feel weak in , students have the tendency to go over the strong subjects again n again this gives them a false sense of hope.
After doing Usmle step 1 once, i recommend taking NBME to know where you stand, and then doing first aid and usmle world one more time and taking a nbme ( i recommend 15 since i was told its one of the hardest one so it gives you a better estimate of knowing whats important)
I think this should do it, for how to study post , if there are any Questions feel free to ask and ill try my best to answer