Set your metronome to a 4/4 quarter note beat and tap your foot as the beat clicks, counting aloud the numbers (1, 2, 3, 4, 1, 2, 3, 4, etc.). Funk bass playing is centered around the beat; playing with, over or slightly behind it creates rhythmic motion and "moves" the song. Also, syncopation and simplicity are key.
Once you have the count in your head and feet, apply it to the bass by finger plucking or thumb thumping the open E (top) string of your bass guitar to every beat, still counting aloud. After a few measures, only play the 1st and 3rd beats. You'll notice that the rhythm changes but the beat remains the same.
Now play the 2nd and 4th beats. This is called playing the "up" beat and sounds, well, upbeat. Introducing the note's octave adds interest to your bassline, so play the 1st and 3rd beats again on the open E, plucking the E octave on the D string's second fret on the 2nd and 4th beats. This creates a "see-saw" effect between the high and low notes.
Mute a note by gently laying the fingers of your fretting hand across the strings and plucking or thumping the note as you normally would, achieving a hollow thudding sound. Muting, sometimes referred to as dampening, continues the funk flavor. Play the 4/4 open note pattern again, this time playing the open E on the 1st beat, muting the 2nd, playing the octave on 3, then hitting the open E again for the 4th beat. Repeat for several measures.
Record yourself and listen to the playback to help you develop your rhythmic skills, although it isn't necessary to master funk playing. Speeding up the metronome or adding fretted notes in lieu of open notes adds harmony to your playing, as does such funk-centric skills such as string beds and slides. Experiment with your basslines and listen to funk players by emulating what you hear to increase your knowledge and playing skill set.