How do I get my shit together? 16F, no life, depressed and chronically online

Nsfw tag just in case, mention of self harm and depression. How do I even start? I don't go to school in person, I go to a hybrid school but I never log on. I have 13 credits as a junior when I should have 18. All I do all day is lay on my ass and scroll through social media, I'm on the wrong side of twitter and I regularly interact with shedtwt (self harm ed twitter), I think its just making my addictions worse. I smoke. Literally all I do is occasionally hang out with friends. I hate myself and jealousy is controlling my life. Literally all I want is an actual life, and I'm almost an adult. I'm terrified that I won't graduate high school and i'll just stay in my mom's basement feeling sorry for myself the rest of my life. So my question is, how do I get my shit together?