Well, lets start with an easy set up (you don't have to go with this, it's just an idea to help kick start your story) -
The protagonist has been trying for years to use this technique, but has only succeeded in learning lucid dreaming. Then he/she finds out about the online course / school and joins. Suddenly, what didn't work before now works.
So, a plot point for you to come up with - what about the online course / school causes this change?
Now you need several more things before you actually have a plot.
First off, you need a protagonist. As you're a guy, I'd suggest a guy, but if you think you're up to it, you could write a girl. So, teenage boy with an interest in dreams and either the paranormal ESP side of magic, or the more traditional type of magic. Again - your choice of "it's magic / it's psychic powers" will affect the type of story and character personalities in it. Magic = mystic, ESP = more scientific. As he doesn't seem to want to meet people in reality it seems likely that he is something of a social recluse.
To sum up: Teenage boy, social recluse, interested in mysticism OR paranormal science.
Your basic template to work on and pad out.
Second step: You need >>>>>***CONFLICT***<<<<<
Without conflict there is nothing to move a story forward, it just becomes "he did, she did, he did, she did," ad nauseum - without purpose.
Now, earlier I said think about what caused the change. Solving this mystery is going to be part of your plot. so having someone or several people trying to stop him from solving this mystery is going to be part of your plot.
However, this is not your whole plot, are even the main bulk of it. You are going to have to brain-storm some conflicts for your story. This is going to be protagonist overcoming an antagonist. So, you need to come up with a antagonist.
Step 3 - expand on your characters.
Cater your character and plot so they match up i.e. someone who's bubbly and keen to get out and see people probably wouldn't match a story about a finding evidence of crime in their secret hiding place and trying to solve the crime herself, but would match a story about trying to blag her way into a VIP area of a nightclub. Conversely, you want someone who's determined, but doesn't have much trust in authority figures, if they're going to solve a crime by themselves. ***
(This is important. As someone once put it - if Hamlet had played the role of Romeo in Romeo & Juliet, they would never have gotten married. It would be a completely different story if a broody neurotic who has to check everything was the lead in place of the passionate head strong Romeo).
+Why is he doing this? The drive of a story is that the hero WANTS something badly. What does your hero really, really, reaaaallly want?
+How will achieving his goal change him forever?
+What is the penalty if he fails?
Do a similar set of questions for your antagonist. A story is a tale of 2 halves - the hero's and the villain's. We may not see all of the villain's side in the story, but it's like an arch, it needs both side to hold it up.
Hopefully, this should be enough to get you going on the right track.