Most new members will have received a little Greetings! message from Discobot when you sign up with some instructions on how to access his first interactive forum tutorial, and there’s also another for his second one when you get promoted to TL2 Member. But if you don’t receive his messages for any reason, or you fancy taking the advanced one before you level up, or even if you just want to enjoy one again, then you can ask him for either whenever you like. 
If his messages aren’t showing up even when you ask for them make sure the box next to 'Skip new user onboarding tips and badges’ is unticked on your Preferences/Interface page.
They’re a great way to learn a bit about some forum features you may not have spotted straight away, and you get a Badge for completing each (the Certified and Licensed ones). And, best of all, they’re really quick and easy.
The Certified one covers things like bookmarking, oneboxing, mentioning, quoting and flagging; and the Licensed one has deleting posts, category tags, topic and category notifications, polls and ‘Hide Details’.
To manually start the Certified one you can type @discobot Start Tutorial in a message below, and that will wake him up.
You should then get a red notification above your profile picture on the top right:
To manually start the advanced tutorial you can type @discobot Start Advanced Tutorial in a message below, and you’ll get a blue notification:
And these are what his messages will look like in your notification list:
Click on those, reply to him as normal doing his tasks as you go, and you should make short work of them. 
If you get stuck you can restart by typing Start Tutorial or Start Advanced Tutorial as a reply in his topic, or you can chuck in the SKIP command to skip a stage.
And if you have any other Discobot questions feel free to ask them below as well.