Practice picking. An easy way to get started is by alternating the pick movement upward and downward several times on every open string. Play with a steady pulse, keeping your strokes as even as possible. Count "1, 2, 3, 4," and tap out the rhythm with your foot. Some beginners might feel more comfortable using only the downward movement of the pick. Now, start developing strength in the fingers of your left hand. Choose a single string and play a different note by pressing with the index finger behind the first fret. Frets are the metal bars on the neck. Remove the index finger and repeat with the remaining fingers, except for the thumb.
Apply the picking technique to natural notes. It is more enjoyable to learn music basics by playing easy songs that you like. For example, the intro bass part of "Another One Bites the Dust" by Queen is made up of the notes E, G and A and can be played on the E string. The G is located on the third fret of the E string, and the A on the fifth fret. The order of the notes for this riff is A-G-E-E-E......E-E-E-G-E-A. Listen to the song and mimic the rhythm.
Practice more natural notes. Natural notes are C, D, E, F, G, A, B. Learn the names of the notes on the fingerboard. It is possible to find fingerboard charts online. The bass player usually plays the root notes of a song's chord progression. For instance, if the song follows a pattern like C-Am-Dm-G7 (as in "Unchained Melody" by the Righteous Brothers, or "Blue Moon" by Rodgers and Hart), the bassist would play the notes C-A-D-G. It doesn't matter if the chords are major, minor, dominant 7th, etc. At first, choose songs with three or four chords and find the root note based on what you have learned. Remember that it is very important to pay attention to the rhythm.