Downloading Age of Empire on MacBookPro

I want to play Age of Empires, on my MacBook Pro. I’m running the latest OS. So... I partitioned my hard drive, using bootcamp, as instructed. The MacBook restarted, loaded Windows 10, as planned. I bought the game online. But, when I try to download it, there isn't enough space on the HD, because bootcamp is taking up 105GB! Why? The partition is half the 256GB I have, but on the Windows 10 side, bootcamp uses 105Gb... so, there’s not enough space to download the game! It seems pointless to partition if there’s no room left? Thanks.