Pick, thumb or fingers - up to you. Google up some videos on floating thumb and adapt them to your 6th string.
http://www.youtube.com/watch?v=PPVMBPmrblU
Just ignore the top two strings on your 6 string electric guitar.
http://www.cyberfretbass.com/scales/basic/page2.php Use the major scale pattern and place the root note on the 6th and or 5th string of your electric guitar.
Most of the time placing the root on the 5th string (3rd on a 4 string guitar) works out for the better. Why? A root placed on the 5th string where is the 4 and 5 note? Above and below your root, is that great or what. C-F-G or D-G-A
Go to
http://www.studybass.com/ Just ignore the top two strings.
This is your basic go to pattern
http://www.studybass.com/lessons/bas...e-major-scale/
On the bass you play cord tones. Music is over a C chord here are your choices:
C -- all Roots, or R-5, or R-3-5-3 why back to 3? If it's 4/4 time you need 4 beats to the bar, going back to the 3 gives you the 4th beat.
C7 - R-3-5-b7
Cmaj7 - R-3-5-7
Cm - R-b3-5-b3
Cm7 R-b3-5-b7
C/something - you play the slash something.
Ignore anything beyond a 7th right at first.
Have fun.