You can participate in Open Access either by archiving your research in a repository or publishing in an Open Access journal.
Archiving in a repository - You can archive your research in UToIR or a disciplinary repository. Archiving is free and allows you to make your work freely available without changing how, where, and why you publish. The majority of publishers allow you to archive the submitted or accepted versions of your articles.
Publishing Open Access - By publishing in Open Access venues, your research will become freely available immediately and typically you'll retain your full copyright. There are over 12,000 peer-reviewed journals in the Directory of Open Access Journals.