Very easy
Use trocador.app for the quickest, cheapest, easiest way
Many more options in the "HOW DO I GET MONERO?" section depending on your preference 👇
https://pb.envs.net/?fddbb02f3599dc10#5o6C51E4iNNQC5APBegEsMRTcDsNcHUFZXEMz6RNbUhq
Discussion
Isn't the Trocadero app proprietary?
Yes, but not sure if open source matters with websites. You can't verify if they are running the same code on their servers anyway.
Best you can do is have no-javascript and/or an onion site. They do both.
http://trocadorfyhlu27aefre5u7zri66gudtzdyelymftvr4yjwcxhfaqsid.onion/
You can also use other options on my link that don't require trust (or minimize trust) like Bisq, UnstoppableSwap, BasicSwapDEX. They are all open source software you can run and verify for yourself.