In general examples are useful though I'm used to having an explanation for every keyword/command which exists in a product.
I thought maybe it exists someplace else, but I understand from your comment that it isn't.
The “add” subcommand occurs for every configuration item where a list of values can be assigned.
There is generic documentation here: https://help.mikrotik.com/docs/display/ROS/Console
It shows you that add/remove/edit/print etc are subcommands present in many contexts, and they are not explained everywhere.
At some point you are presumed to understand that “add” will add an IP address. Or a route. Or whatever.