ICloud, how do I download apps to it?

I've ran out of memory on my iPhone, I've purchased 10g of additional space on my iCloud and I want to download an app to iCloud. Can I use it as additional memory because even tho I have nearly 15g space on iCloud, I can't download an app to it.

That's because you can't download an app to iCloud. You can only download ANYTHING to a device.

Just back up those apps which you use rarely on iCloud and free your fone space. Then download and enjoy latest ones… Also you can delete your purchased apps for new ones. You can download those apps again under the same account since you've already paid for those.