If you're a beginner bass player, sometimes the best way to learn is to watch others play. Also, learning from books and virtual bass websites can be frustrating and confusing, but this video makes it all simple. It's a beginner bass lesson for "Tush" from ZZ Top. It's basically a 12-bar blues, and there are 2 different bass lines to this format— either the verse or what's played under the guitar solo.
All of the lines are played slowly with a metronome and then the notes are talked through in some detail, including note names and also fret locations.