Learn to mange permissions for your server
FredBoat's permissions can be configured the same way as any other Discord bot which uses slash commands. If you have both the Manage Server and Manage Roles permissions in a Discord server, you are able to define which Discord users and roles are allowed to use which commands, and in which channels. You can define permissions in the Integrations menu of the Server Settings. Then click Manage next to FredBoat. See also Discord's guide.
If you have the required permissions and you still do not see any slash commands from FredBoat in the settings menu, you may need to grant the bot permission to create commands in your server.
By default, all slash commands can be used by everyone. The only exception to this is the /config which by default can only be used by people with the Manage Server permission. Additionally, users can only execute commands if they have the Use Application Commands, which the @everyone role has by default.
In FredBoat, slash command permissions do not only affect a user's ability to run slash commands. Slash command permissions also affect legacy commands and the dashboard. For instance, if a user does not have permissions to run /play then they also can't use @FredBoat play or add new tracks through the dashboard.
Before slash commands were introduced, FredBoat had a different permission system with predefined levels. This system has been completely removed.