Like Ron G said; a major triad is the root note, the 3rd note of its major scale, and the 5th note of its major scale. Commonly written as R-3-5.
Example: C major scale is C-D-E-F-G-A-B-C
Root = C
3rd = E
5th = G
Take that major triad and instead of fretting the 3rd note of its major scale, fret the pitch lower by a half-step and you have a minor triad.
Using the C major scale, a minor triad
Root = C
3rd = E flat
5th = G
Use a metronome and set the tempo slow. Begin feeling where you want your bass line to lay. When you have it grounded and can feel the groove, begin to experiment. Throw in a triplet on whatever beat you want.
If it sounds good to you awesome
If it sounds bad to you, no worries, try something else
Most of all have fun!