Applying to internship postings is great but sometimes there are not a lot of them. Reach out! Contact the agency, company or nonprofit directly. Not every place advertises their internship opportunities. Also, a lot of places are willing to have an intern. You can create your own internship.
Send an email. In the email, start by introducing yourself and education details. Next, explain your interest in doing an internship at the agency, company or nonprofit and ask if they have internships available. Be sure to state when you want to do this internship (i.e. summer or fall).
Make sure to attach your resume. If possible include a cover letter and writing samples. Be patient it can take days or even weeks before you get a response.
Sometimes to land an internship you have to get creative. The worst that can happen is the place responding that they do not have internships available.