Where and how do I buy parking tickets online?

You can't each lot has different owners most only want cash

I use the Parking Panda app on my phone; it gives you all nearby lots and you can pay in advance. I just paid $17 for game on April 8 vs Baltimore, just a short walk from the stadium.

I haven't found it online either. Its bit of a mess there also. Seems like every lot has different people running it.