Multiselect has one setting, “Multiselect Options”, a textarea in which you specify each option you want as part of the multi-select.

List one option per line:

Herbie Hancock
Miles Davis
The Beatles

You can optionally specify input values for each option, and organize options into optgroups:

    herbie : Herbie Hancock
    miles : Miles Davis
    beatles : The Beatles
    bobby : Bob Dylan