You can take online classes for certification from several sources including Google and Microsoft. Edx.org is a great source of free classes and inexpensive certifications.
Once you’ve learned the material, develop a portfolio of projects that you can write about on your resume and cover letter. In the meantime, look for entry level jobs for companies that employ SWEs and, once there, you can seek out opportunities to meet people and learn more about what skills are in demand. Some companies will also assist with training and college courses.