AFAIK, BTC is the only crypto traded on bisq, so it shouldn't be the problem for you to sell BTC there. As for how to use it, I have to say it's not the rocket science. Just install the app and spend couple of hours getting familiar with how it works by following the available guides. In addition to bisq, there's also bisq2, which is quite different platform that requires other app . You can install both and try them out to see which one suits you better.