By now you would be aware that whatever position you are playing in you will need to change position in order to play certain notes. By mastering the Ninth & Tenth positions you will be able to extend your playing and sight reading abilities to encompas the neck up to the 13th fret. No Mean Feat ! and one which will take some time get comfortable with.
Remember, positions are simply the fret that the First finger plays on. eg if the first finger is playing the note "F" on the second string, that would be the 6th position. While playing in this position the First finger would play all the notes in the 6th fret, the Second finger would play all the notes in the 7th fret, the Third finger all notes in the 8th fret and the Fourth finger all the notes in the 9th fret. Of course if the music indicated notes outside this position a new position would be required.