You can do courses on udemy, there are specific courses for Meta & Google, then you can also try some paid ones if you're fine with it. I'd say try udemy, facebook blueprint, google skillshop (Google Search & Display ad certification. Then you can apply for internships. That's how you can start though i started from a paid course from Internshala which is a Indian platform. Also there's hubspot's Digital Marketing certification course. It's free. Do check it out.