Are you asking asking what notes make up a chord?
I will answer that question anyway, as that is the only think i think you could mean.
If this does not make sense I am sure someone else will be able to explain it better.
If you already know this I guess I wasted my time.
you know the chord is named after the root, in your example, that's C. The major chord is made up of three notes...the root, its 3rd and its 5th. To find them, look at the scale for that chord and find the 3rd and 5th notes.
for our example that is E and G
what you said "C (being root) next is E and then C on the B string" is right you have two of the notes needed to make this chord. The last one is the open G string, that will make your 5th.
now that you know what notes make up a C chord you can make that chord how ever you like. as long as it uses those three notes you are good.
and it doesn't matter how many times you use them either... that's why you have 2 Cs in your chord and not have it effect anything.
keep in mind this is just for major chords, you can go, way,way way, more into it than this.
chances are you already knew this and I just wasted my breath, but Im over it, its all good.