Ok, so the only way is exchanging money? How adding money to the network was done before there was enough bitcoins?
From the wiki, you will see that:
New bitcoins are generated by the network through the process of "mining". In a process that is similar to a continuous raffle draw, mining nodes on the network are awarded bitcoins each time they find the solution to a certain mathematical problem (and thereby create a new block). Creating a block is a proof of work with a difficulty that varies with the overall strength of the network.
You may read more about it here:
https://en.bitcoin.it/wiki/FAQ#How_are_new_bitcoins_created.3FThere is also a Mining category (
https://bitcointalk.org/index.php?board=14.0) here so that you can see how people actually "mine" bitcoins.