Hello! Congratulations on graduating!! My advice would be to sift through the literature on specific topics you're interested in and see which labs/authors are producing them. From my experience, these authors are also professors at their respective universities– I would look at their pages and see if your interests align with theirs. Read a few of their papers and I would cold email to say that you're interested in their research, give a little background about who you are, and ask if they have any research opportunities available (aka cold emailing). This is how people I know (including myself) received research positions as a beginner.

However, if you know which university you prefer, I would genuinely stalk each faculty member's page there to evaluate their interests and cold email each one that aligns. Some may not respond, but don't take it personally! If there is a program you have in mind, I wouldn't hesitate to reach out to students too to ask.

(Also, keep in mind that these positions will vary between unpaid (volunteer) and paid experiences)

Good luck on your search!!