This is the very first bass lesson I posted and I'm pleased to say, it has helped hundreds of thousands of beginners get a grasp on music theory and start their journey with playing bass guitar.
Thinking in terms of shapes will help with your improvisational skills. Try this lesson and then try to apply it to the chart lesson.
Here's a lesson on how to read a chart. This is where knowing about music theory, scales, chords, etc. comes in handy.
Bass harmonics is another technique you
can use to create music. Using harmonics is also a good way to tune your bass​.​
Step up your bass skills and incorporate
ghost notes ​into your playing. Ghost notes
add a percussiveness to the groove.​
Chords... sometimes overlooked by bassists, they are extremely important
​for a bassist to know. Knowing how chords are constructed will help you create better bass lines. 
Playing the blues is a must for bassists. It's a great way to develop your feel and groove.
Doing exercises in different time
signatures helps improve your chops. Here's one in 3/4 time.​