Newbie! I'd love some tips and advice!

Hey! My name is Mykal (Makal, as in california) and I'm 21. When I was a freshman in high school, I was a size 0 and couldn't find anything that fit me right. I was not a fan of my metabolism at all and people always told me to take advantage of it and be grateful. It was so hard. When I was a senior in high school, I finally started to fill out and by the time I was a sophomore in college I was a size 14 and I couldn't believe it. I would habit fully buy small and medium tops and have to return them because they were too small. I was heart broken. I finally looked at myself in the mirror and I was devastated. I felt fat. I felt terrible. My arms are flabby, my stomach is flabby, and I have stretch marks everywhere. I'm done feeling bad about myself and it's time to change and get fit!! I need to stay motivated and learn tips and tricks!! Help me out, friends!