Welcome to the site and to the hobby! There are many games on the Looking For Group listings which welcome new players. There's even a filter button just for that purpose. My biggest piece of advice is to be patient when looking to join. There are many more people looking to play than there are gamemasters, and it may take a number of tries before finding an open spot. Folks here on the forum can be very helpful, though the terms of usage restrict the conversation to Roll20-specific topics. It sounds like you've got a good intro to D&D through the podcasts available out there. It's a great leg-up that did not exist back when I started in the late 70's. :) I would also suggest looking through the Roll20 youtube channel. They have many recorded games that will not only showcase D&D and RPGs in general, but help you get a feel for how the site allows you to play.
