Changing custom header/logo position

Hi!

I’m putting together a website for someone else using the Ever After theme and I’m trying to change the logo positioning to the left side of the page. I figured it out with ease the other day, but the CSS decided not to save, and now I can’t figure it out again for the life of me. Changing the margins is suddenly not working for it, which I’m positive is what I did to fix it in the first place. I’m not sure whether I’m trying the right code but just in the wrong place, or I’m just remembering it all horribly wrong. What am I missing?

Thanks!