Say if i needed to play a scale e.g. Locrian in C, how can i play this on the third fret as well as the 8th? Thanks
Figure out the notes and find them on the fretboard. C Locrian has the notes C Db Eb F Gb Ab Bb. Anywhere on the neck that you find those notes, you can play C Locrian.
C Locrian contains all the notes of Db major. If you can learn the major scale, you just need to play the Db major scale at the 3rd fret.