You've played D&D before. You don't need to be taught the rules. You just want to get into the action. You might want to go back to the campaign packages, but if you insist on a single session, you can expect the following:
Three to four hours of play.
Choose any of the following for your character:
Choose one of sixteen pregens.
Send your preferences to the DM and have a custom character built for you.
Take the reigns and create a character in D&D Beyond with temporary access to DM Josh's materials.
Choose from a list of adventures, including popular published content and some of Josh's own creation.