Just google " free hosting " and it will come up with some hosting sites that will let you upload the file.( that is found under SI/FM13/Games. Try use one of the hosting sites that don't require you to register to download a file though ( registration might be needed for the upload though)
find the save game in Documents, Sports Interactive, Football Manager 2013, games

then put it in a zip file or a rar file so it's a smaller file size then you should be able to upload it to somewhere like mediafire. Not sure exactly where will work as they all have different file size limits, which I don't know and depending on how far through the save you are and how many leagues and players are loaded then the file size of your save could vary quite abit.
What sammyt said about Mediafire, but you can compress the file on the game itself via Preferences -> Saving if it's to big to upload. Registration is required there to let you know.