anyone who know music theory care to tell me or show me something

>>42413
Basically, unless you're actively looking for dissonance (ie bebop or avant-garde jazz stuff), all the notes in a chord (2 in a fifth, 3 in a major/minor/diminished/augmented, 4 in a 6th and 7th, 5 in a 9th, 6 in an 11th and a 13th. When you play, say, a major on a guitar, you're playing the same note in a higher eight, 2 or 3 times) are to be found in the same scale that the melody is using. That creates harmony.

As for how to comprehend what chord progression you should use on a melody... see this:
https://www.youtube.com/watch?v=fXIEmMDwc7E

Hell, just see all the videos in the series. It's like only a bit over an hour in total, and this lady is actually quite good at teaching the basics of music theory:
https://www.youtube.com/watch?v=HBwHXssyHZ0
https://www.youtube.com/watch?v=WgP1Zk04shk
https://www.youtube.com/watch?v=0I49c0TSkHs
https://www.youtube.com/watch?v=rt6zDOFNAdY
https://www.youtube.com/watch?v=KWLb9ivZKnc
https://www.youtube.com/watch?v=cpheIZP9Rss
https://www.youtube.com/watch?v=fXIEmMDwc7E
https://www.youtube.com/watch?v=fqGKVjPnHlY