Hi Abderrahim, welcome to the community! Richard did a club session on barre chords. There is not a recording of the session, but he did provide a great downloadable resource that gives an introduction to barre chords. Click on the orange Download button. Given that you are not familiar with barre chords, it may take some time to absorb the material.
Also, we’d love to hear more about your guitar journey. Consider introducing yourself over here!
Don’t worry! Its been ages since I wrote this but the barre chords part is a bit of a red herring (although not really). Try the same pattern with power chords, it works the same.
The point i think justin was making was the pattern the I-VI chords in a key have on string 5 &6.
When you know your e and a shaped major and.minor barre chords you can use the pattern too.
@Hopeypooze sorry for the very late reply …
I wasn’t notified …
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@jamiab96 also …
Barre chords in their bigger sense are Grade 3-5. You do learn F in Grade 2 and it is the first (perhaps) most difficult barre chord grip.
Look for lessons on E-shape and A-shape barre chords.
Plus @judi has linked to some resources I created which can help.
I see, since I’m trying to go through the music theory course I’m more interested in trying to understand how it is constructed from a theory standpoint, so far in the practical music theory course when it comes to chords, Justin talks about triads, and open chords. I still have no knowledge on how a chord works when strumming more than 3 strings. And thank you and @judi for linking the learning material on barre chords, I’ll definitely check it out 
I see, thank you for the quick reply, I’ll try to focus on the main topic then, my progression was pretty steady up to this point! 
I get it, the sudden barre chord thing almost derailed me too. Don’t let it, it didn’t turn out to even be that important, more of a cool tip for when you play barre chords. I also didnt want to move past it while I was confused because up to that point there is no “fat” in tbe theory course. Its not really fat but its not an essential building block. It made sense to me later.
Anyway, barre chords are just the notes in the chord, just like open chords are. Its just a way of playing them (and a whole lot of other CAGED hoo ha which is why they seem confusing, because its made to sound confusing) but theyre just chords.
As i recall the point of the lesson that almost killed my confidence was degrees of the scale , and chord progressions using that info. As long as you understand MmmMMmDim youre golden.
I’m glad to hear, I just wasn’t sure if I had skipped something important along the way before that lesson in the module, or if maybe I should’ve just gone through the intermediate/advanced regular courses first in order to start the practical music theory course.
I’ll just focus on the chord progression, thanks once again