Opening the configuration screen depends on the application and sometimes the operating system you are using.
As a shortcut you can press Ctrl+, on Windows and Linux, or Cmd+, on macOS.
In the menu, click on Tools > Options.
Or press Ctrl+,.
In the menu, click on Joplin > Preferences
Or press Cmd+,.
Tap on the burger icon ≡ in the top left corner, and select Configuration.
Type :help config
for information on how to set config values and for the complete list of available options.
Type :config
to list all of the currently-set options and values.
Type :config [option] [value]
to set [option]
to [value]
.