This is a tricky one. :eek:
What makes guitar unique (and ultimately frustrating,) is that you can play multiple notes of the same octave in several places! Reading music pertains to all instruments, but it starts for many people with the piano. On the piano, every note and it's octaves can only be played in one spot. That's it!
It really pertains to "what" you are playing. For example, middle C on the staff is the 3rd fret on the A string of the guitar (an octave lower then what's played on a piano, as it's transpositional.) You can also play that note on the 8th fret of the E string. It can be tricky to know "which" note to play. I recommend first knowing where all those notes are, then take a look at what you are reading and decide which sounds best with the other notes.
When you are beginning to learn how to read, you typically will learn things in open position as you have already. Once you feel comfortable with a particular passage or piece, try playing it somewhere else on the guitar. From there, decide what you think sounds best and go with that. It's good to practice all the possibilites and from there, dictate what's the most appropriate.
Reading for guitar isn't easy for anyone, but it's a great skill to have no matter what the style or approach you take to the instrument. Hopefully this was helpful. :confused:
Douglas Showalter