Have you checked the RoboFab site? The RoboFab documentation at http://www.robofab.com/objects/index.html is pretty good.
As regards kerning, see especially http://www.robofab.com/objects/font.html and http://robofab.com/objects/kerning.html
I haven't used it for some time now, but in a RoboFab font object, kerning is a dictionary which you access like this
# import the font class:
from robofab import CurrentFont
# turn the current FLS font into a RoboFab font object:
f = CurrentFont()
# get at kerning in the current font:
kerning = f.kerning
and then you should be able to either directly add kerning to this kerning object/dict like
# note that the key is a tuple:
kerning[ ('glyphA','glyphB') ] = 10
or, alternatively, create a new temporary kerning dictionary which you feed with additional kerning pairs, and finally update the font's kerning dictionary with the new one
newKerning = {}
newKerning[ ('glyphA','glyphB') ] = 10
kerning.update(newKerning)
and don't forget to update the font
f.update()