Subcommands take options, which start with --.
See all options and their purpose with aws <command> <subcommand> help.
While most are optional (hence the name), those that are not surrounded by square brackets ([]) are required. You will get an error message (with appropriate details) if you do not include them.
The built-in documentation is the best place to start looking for answers. There are usually examples after all of the options have been described. Otherwise, there are plenty of examples available online.
Some options are available to all or most commands, so they are particularly useful to know.