Scratch

You can't really get TAUGHT, but you can get advice. And here is mine:
Fiddle around with the Scratch blocks. If you don't understand some of them, ask people how to use them, or right click (Control click if you have a Mac) on the block that you are confused with, and a menu will show up. Click help, and a box comes up explaining how to use that block.
If you don't want to do it this way, try looking at other Scratchers' Mario Bros projects. Download them, and that way you can see their scripts so if you need help you can just look at their scripts.
If you have a really bad bug in your project and need help getting it fixed, then you can upload your project, post a topic in the forum about you needing help with the bug, post the link, and people will probably help you.
I am not a pro at making Mario games (I haven't even tried, they are probably complicated), but I have some tips for you:
1. Have good graphics. People wouldn't want to play your game if your Mario was a stick figure with a red hat, or your goombas were brown blobs. 
2. Try to fix all your bugs before uploading your project (Unless you are uploading it to show people the bug/bugs and help get it fixed).
3. Make sure it works online. I don't know why, but it is always better when it is online. I think it shows that if it doesn't work online, it has too many bugs or something.
4.Add some music! Your Mario game isn't complete without some classic Mario music (Note: If you are going to do this, you might want to add in a button to stop the music)! 
I hope this helps!