Honestly that is probably the worst way to practice for online Nascar racing. The only way your going to learn is to just jump in a room. Let them know you're knew and most good racers will understand and help you along. Just run the basic setup you find in the oval tunery to start with and when you get the hang of it you can start playing around with different settings.
https://www.gtplanet.net/forum/showthread.php?t=215767&highlight=oval+tunery
Just a few pointers (I've been racing Nascar online since this game came out);
Basic etiquette is not to pass under the yellow line unless you are forced to. And if you do give the position back if it's safe to.
If you can't hold your line drift to the back and ride around till you get a feel for it.
Don't be afraid to let out of the throttle mid corner to keep from slipping under someone's quarter panel, (number one cause of wrecks) you will catch them on the straight in no time.
Along the same lines don't be in a hurry to get to the front. You can ride half throttle behind others for quite awhile and still win the race. It's easier to ride around for a bit than to try and catch the pack from a straightaway behind after you're done spinning.
Above all else just be respectful to the host and others and you should be fine.