The internet bandwidth will be divided up based on usage. If there are only two computers on the network, each one will get 50%. If there were 3, each would get 33% (roughly).
If you want one computer to have more bandwidth, simply keep the others off the internet for that time being, and that one computer can utilize the full bandwith. Also, if there are two computers (or more) on a network and only one is active on the internet while the others are idle, then that active computer gets most of the bandwidth. Otherwise, they have to share.
As far as I know, there is no "power distributor" for network bandwidth. I suppose you could control it like electricity and dial it up or down (with the right knowledge and equipment), but I do not know of a device that does this. It sounds remotely possible in theory, but I've never heard of it being done before.
Does that answer your question?