im learning xrpl, but im confused about how to get xrp into a private exchange?
https://xrpl.org/become-an-xrp-ledger-gateway.html
"A Private Exchange holds XRP and lets its customers buy and sell that XRP in its own system. Most cryptocurrencies rely on private exchanges to provide a market for the cryptocurrency, but the XRP Ledger has a currency exchange built into the protocol itself."
where does that xrp come from?
On
First, you need to get an idea how ripple works. XRP Labs are the foundation responsible for development of XRP and it is not for profit. They provided a fixed supply (100B XRP), almost have of that is in circulation currently. There is no mining or stacking in XRP.
On the other hand, Ripple is a for profit company and the provide a liquidity solutions for businesses. So, you need to seek a partnership with them. Other options would be signing up for one of XRP exchanges like Gatehub or Bitstamp. Also, the great thing about Ripple network, is that it a decentralized exchange by default. So, once you have a liquidity (of any available currency), you trade with a decentralized exchange like sologenic.
The link you've posted is for exchanges and not for end users. Exchanges get XRP from users. Users transfer XRP to the exchange and trade it there! So the exchange just have to setup the wallet and users can start depositing and withdrawing XRP from exchanges! (If the exchange is responsible enough, they'll even setup their own node and actively maintain it.)
Your question is not very clear to me. If you can rephrase your question I'll try my best to help you.
If you want to learn more about XRPL you can check this: Xumm Developer Education.