Help!! How to fatten up a hedgehog ?

Hi there,  i have 2 hedgehogs that visit me nightly for about almost 2 months and there is a big field outside my back garden and last night i found this little hedgehog,  well little compared to the 2 hedgehogs that visit me and im not 100% sure but i think this could maybe be a baby.. so my question is how fo i fatten this little baby up in time for hibernation my friends?  Do i need to bring him indoors.. i didnt want to lift him last night and do anything until i got some advice as i dont want to cause any harm by moving him obviously!  Im happy to search this massive field day and night until i find him to fatten him up if need be... thanks guys for any advice.. Xx