About digital tv! i have not got a digital ariel yet but have sky downstairs!?

all of my tvs upstairs do not work cause i they are not connected to sky...what do a need to get for them to start working, a cant afford to go digital at the moment! i have seen digital receivers but not sure if they will work with me not having the ariel changed to digital.....never had a freeview box so dont know what they are neither...does anyone know what i need to do.