I'm stuck with apart in the above lesson.
Can anyone explain a bit more above the part below?
How and what do you add to get the results? I'm completely confused with it and it's starting to bother me.
Can some one maybe write a another question and explain it or something?!

01.Start with the note C.
02.Add a note a Major 3rd above C, which is E.
03.Add a note a minor 3rd above E, which is G.
It's telling you how to make a C major chord. Major chords are constructed by taking the 1st, 3rd, and 5th notes of the major scale and playing them together. Similarly, minor chords are made from the 1st, 3rd, and 5th of the minor scale.

If someone talks about a major third above/below something, they are talking about the note which is 2 whole steps away (4 frets). The note 2 whole steps above C is E (02).
A minor third above or below something is 1 1/2 whole steps away. If you start with E, the minor third is G (03).

Now going back to all the notes of the major scale. The distances between all the notes go like this starting from the root.
Major second (root + 1 whole step).
Major third (Major 2nd + 1 whole step).
Fourth (Major 3rd + 1/2 step)
Fifth (fourth + 1 whole step)
Major sixth (fifth + 1 whole step)
Major seventh (major sixth plus one whole step)
Octave (major 7th plus a half step).

02 should be clear by now. 03 - since it is 1/2 a step from the major 3rd to the 4th, and a whole step from the 4th to the 5th, this adds up to 1 1/2 whole steps - a minor third. So if you go up a minor third from the major third, you get the 5th relative to the root, the final part of your major chord.

Hopefully that makes sense. It basically another way of saying take the root, third, and fifth to make your chord.