common eight bar blues chords/explanation for beginners

For those of you who don't know, a chord is several notes played at the same time. Certain songs (almost all) have chord progression. it would look something like this, I IV V I. Each of those roman numerals translate to certain note in the major scale. The note that it translates to is called a tonic and that is the lowest note in the chord. So essentially the roman numeral "I" means the number 1 which means the first note in the major scale (c or holes 1 and 4 on your diatonic c harmonica). From there, you can build your chords. 

For instance, the progression of an 8 bar blues could be I(1) V(5) IV(4) IV(4) I  V  I  V

First bar=I(1)
Blow into the holes, 1  2  3

second bar=V(5)
Suck through holes, 2  3  4

third bar=IV(4)
Suck through holes, 5  6

fourth bar=IV(4)
Suck through holes, 5  6

fifth bar=I(1)
Blow into the holes, 1  2  3

sixth bar=V(5)
Suck through holes, 2  3  4

seventh bar=I(1)
Blow into the holes, 1  2  3

eighth bar=V(5)
Suck through holes, 2  3  4