This is a great question. It might seem tough to sell a psychology degree, arguably a 'soft degree,' however, there are a lot of HR reps with BS in psychology. The only problem is a lot of people are vying for such positions so it's up to you to stand out. My top tips would be:
If you do not have any professional office experience, apply for administrative assistant position or office contract positions to build your resume. Employers want to know you can handle multiple projects, and different tasks so brush up on your time and project management skills and really stress that in your resume. Put class projects if you do not have any direct work experience yet
Network: Always important. Who do you know (but more importantly, who knows you). Find someone in an HR field and see if you can intern or shadow with them to gain applicable experience.
Highlight your current experiences with in your degree. We as psych majors learn how to speak to people. We know that an individuals thought process shapes their behaviors, so we act accordingly. This can be shaped in an interview, "I've worked with people from diverse backgrounds, and I have the ability to communicate accordingly to a wide range of people to garner buy-in when dealing with a project that might conflict with the priorities of those involved."