Catfish questions.....?

well i been searching on youtube on channel catfish and i was wondering why do people use bobbers i thought they were bottom dwellers and the line don't even that far and plus im gonna go fishing at a river, should i use a bobber too? and as bait, berkley power bait catfish bait don't work at all, fishing a whole day without a single fish and i don't know if it was the river or something else and yes i got chicken liver today and tommorrow i will try catfishing again and will the chicken liver work, a guarantee fish, at least one catfish will bite right?