The numbers, sharps and flats are figured bass. Any note without a figure under it is assumed to be a root position triad. a 6 is first inversion (a 6th above the bass). A "#" means the third is sharped above the bass. If you play baroque keyboard, you have to be able to read this stuff the way jazz pianists today can read a lead sheet. If you are just playing the bass line, you don't do anything different than if the figures weren't there.