Think about your EC’s a bit later. You may look for some like volunteering, but focus on your academics to begin with. With established high college GPA, it is not that hard to find internships at your college, it may take just one email to a person in charge. So, one step at a time. And make sure you live a balanced life and manage time effectively. If you were involved in many un-related ECs in HS, it is a bit plus as you got that time management skill already. Get involved in college life, find your “circle of friends”, you will need a lot of support away from home.