How to add support for private slash commands

Not a big Discord user so lots of common stuff I don't know. But I've made a bot for use just in one channel with a couple of friends. I have slash commands working and I've experimented enough to send and receive DMs.
But now I want to add support slash commands in DMs. I can't seem to find the next step via Google, the official docs, Stack Overflow, searching this discord, or asking AI chatbots.
Do I have to modify some stuff on my bot's dev page? Pass some more settings in new Client() in my bot code? Or both?
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