Monero was launched in 2014, and its goal is simple: to allow transactions to take place privately and with anonymity. Even though it's commonly thought that BTC can conceal a person's identity, it's often easy to trace payments back to their original source because most blockchains are transparent. On the other hand, XMR is designed to obscure senders and recipients alike through the use of advanced cryptography.
To be able to buy funds from these DEXs you need to have a wallet. I personally use https://www.exodus.com/ because it's got a wide range of coins, is user intuitive and most importantly non-custodial. not your keys, not your coins.
... WiP