You can't - Fuji instant film only comes in pack form, not single sheet. You need a PA45 holder for the Fuji pack film.
(The PA45 holder works as well with the 4x5 as any instant pack holder - i.e. it works great when it works, which is most of the time, but when the extractor strip tears off one sheet when it shouldn't or one of them gums up the whole bloody works with 8 sheets still inside the holder you'll want to throw it across the room.)
I understand that Fuji Quickload/Kodak Readyload 'normal' (i.e. not instant) sheet film works in the 545, but as there's no pressure plate you may have film flatness/critical focus ishoos.
Otherwise, as mjs says, it makes a nice paperweight. My 545Pro will be reduced to that soon
