Did you also get a PFD and fins..? You are required to have a PFD at all times.
So if your all set, yeah a lake would be good, you will need waders, as most all lakes do not allow humane contact with the water, plus it's getting chilly, or it will be..lol
I would not recommend HH, as the current there can be pretty strong for a newer person, NPH or the LAB would be much better. NPH around the docks is always pretty calm, unless there are real strong winds blowing.
The hardest part is getting use to steering with your fins, i.e. going in a circle, or turning in tight places. When you first get in the water, experiment by kicking just one fin, then the other to get an idea of how they work, it's pretty easy once you get the hang of it, I mean seriously, if I can do it, anyone can..lol
Just remember, you are now able to get closer to the fish, slashing, i.e. kicking your fins, and moving about can and will spook the fish, so try and be as stealthy as possible. Anyhow, good luck, and have fun.
Oh, and Don't lean forward on your tube, it won't end well..