Most of our music: rock, jazz, pop and classical is derived from the major modes. So, if you master the major modes, you should be, technically, in very good shape!
The modes are different degrees of the major scale. Meaning that if you play a C major scale starting from its second degree: D (D, E, F, G, A, B, C, D) you will be playing what we call the D Dorian mode. If you start from its third degree: E, it will be called the E Phrygian mode, etc. etc. The modes were originally created by the Byzantines and then passed on to the Hebrews and to the Greeks. The names of the modes came from the ancient Greek modes, later renamed by the Romans. The Greek modes were not played in the same order as the ones we are using today, and some of the names were slightly different. We only keep the names as a numerical form.
The Ionian mode is used to play over Major chords (Major, Maj7 or 6th) only when it is the key of the tune. The Dorian mode is used to play over minor chords (Minor, Minor 7, Minor 13 or Minor 11). The Phrygian mode is used to play over minor chords, only when it is the third of the key. The Lydian mode is used to play over most of the Major chords. The Mixolydian mode is used to play over Dominant 7 chords (7th, 11, 13). The Aeolian mode is used to play over minor chords, only when it is the relative minor of the key. The Locrian mode is used to play over Minor 7 flat 5 chords (m7b5) or Half Diminished.
Practice these modes remembering each individual pattern, to be able to play each of them from any note on your bass. Example if you have a Cm7 chord, you will play C Dorian (C, D, Eb, F, G, A, Bb C).
Don't forget to apply the technique of your picking hand that you learned in the first and second lessons. The numbers above the staff are for the left hand and below for the right hand or picking hand. Reversed or course if you are a lefty. You will notice that the position for the left hand ascending fingering is different from the descending fingering. Have fun!