My rabbit is pregnant for the second time?

my female rabbit had her first litter a couple months ago but they died and someone said the first litter wont make it because the mother does not know how to take care of them is that true? well my female rabbit lemon just bred again with my male rabbit named mr.whisker and im wondering should get a cardboard box and let her use that has a nest box because i bred rabbits all my life i just dont know what i should do to help my female rabbit on her second litter i need some advice please help me please !