The first step is to find a suitable journal. The DOAJ (Directory of Open Access Journals) or Cabell's are places to start to find vetted journals. If a journal is not there, it may still be open, but should be carefully evaluated. Such journals often are either too new or do not meet some of the strict criteria imposed.
Evaluation criteria you might want to consider include the journal's profit model, peer review process, journal metrics and impact factor, and the credentials of the editorial board and previously published authors. A librarian can help navigate these choices.