Put down chux, the pee pads they put under people in bedridden situations. You can get them at Amazon, pharmacies, medical supply stores.
Or purchase puppy pee pads. Purchase anywhere pet supplies are sold.
go for the chux, my girl kitty is 12 now and feeling her age, she prefers the chux
I would not encourage this - dogs will then urinate on any thing inside. Best to get them going outside.