There's a few ways to go about doing this, with the best one depending upon your situation.
Personal contacts: An example of using your personal contacts directly would be asking any PAs or MD/DOs you know if you could shadow them, even if it's your primary care provider or someone you meet in an urgent care. Just ask! Using your personal contacts indirectly is asking friends, family, girlfriends, professors, even PA programs, if they know anyone who is willing to take on students. Three of my shadowing experiences were through the personal contacts method.
Cold-calling: During COVID, I was really, really, desperate for more shadowing. I had a ton of online shadowing hours, but the pandemic was coming to an end, and most programs didn't take online hours at that point. I went on LinkedIn, messaged around 100 PAs, got a response from several, and ended up shadowing one in trauma surgery. You can "cold-call" by sending a DM on LinkedIn, Facebook, even Instagram to a PA in your area. You can also literally cold-call offices and ask if they'd be willing to take on a student (private practices and private surgery centers are your best bet).
3. Through your PCE: Another excellent way to gain shadowing hours is through your patient-care job. If you're a Pre-PA student, you should already have a PCE job anyway. If you don't, get one. Right now! A great way to do this is through Advanced eClinical Training, through one of their online medical certification programs. I personally always recommend the medical assistant program, as the knowledge and skills you learn through the online course and as working as a CMA are invaluable in PA school and when you start clinical rotations. For $100 off, you can use code "Christian100" here. Odds are, there's a PA or MD/DO at your office you can ask if you can formally shadow.
I'm having a hard time finding PAs to shadow, any advice ?