if you have a chord progression you should find that all the notes in the chords fit into one or moe of the basic scale shapes eg majour scale. when you play your progresssion try to work out by ear which chord is the 'root' chord. you will probably find it is the chord you start on. if it is for instance G majour play the g majour scale shape, and if it is Eminor play the Eminor shape. this is only a ruff guide and if you use more complex chord progressions you might find it a bit limited. its not that the theory isnt complete just that it gets far more complicated so for now do the above.