what should i do in my remaining 2 years to make myself college competitive?
i am a highschool sophomore
Now is the perfect time to start considering this!
As far as tests go: in your junior year, take the SAT one or two times, so that you don't need to take it in senior year (or if you want to improve, you'll only have to take it once as a senior). If you are ready, take SAT subject tests! Particularly if you are interested in STEM, having at least two SATII tests in your preferred subject (usually Math 2 + a science) is preferable.
Classes: take the most rigorous classes you can handle. If your school offers courses that match your preferred career path/major, then prioritize those. Keep your grades up.
Extracurriculars: This is so important! You want to make sure you get this started in 10th or 11th grade. What are your passions? Is there a club or activity where you can take leadership in? If not, can you establish such a club/activity? Colleges want to see that you have specific interests, and that you have been proactive in enriching yourself in this way. Start something new. If an internship applies somehow, seek that out. I can't really give specifics because you asked a very general question
Evidence of humanity: Keep your non-school life rich as well. Get a job or volunteer (community service). This shows responsibility outside of a controlled environment. If you want to write a good essay in a couple of years, as well as be able to readily answer questions during interviews, become reflective! Make a habit of considering how your experiences are affecting you and other people. Write regularly. The better you understand yourself and your life, the more easily you will be able to express that to colleges in essays and interviews.
It's good that you're thinking about this now! You got this! Please do update with more specific info, as @alyssa33 said above.
@isabelringing2 just gave you a fantastic answer, there really isn't too much more to add on-top of what they said unless we have more specific information. Since you're a sophomore now, I would try to prioritize your ECs if possible. Sometimes students realize a bit too late the importance of ECs and scramble to try to find things to put on their application. If you start working on your EC profile now you won't have to worry about that once you start applying.
If you have an idea of what you want to major in in college, try to find ECs that compliment that major. Not every EC has to be related to your interests but it's a good idea to show schools you are serious about your passions. You don't need crazy accomplishments in all your ECs either, but showing dedication and leadership in a few is important. While you're not expected to be the president of every club you join and to win every competition you're a part of schools will still want to see that for some of your activities. The good news is that you still have plenty of time to work on all this. If you update the post with more info about your interests I can try to give you more specific steps to take!