Fledgling sparrow

Hello all,

yesterday at around 3pm I found a fledgling sparrow in the boiler room. We think it fell down from a nest in the roof. But when we looked for one we couldn’t find one. I have build a little cage with nest material and paper towel. I have fed it mushed up wet dog Biscuits as that’s what google said to do. It is still healthy today. I don’t know how long till it can fly or what to feed it now. Any advice would be appreciated