The mixing yellow can be used like... a yellow : alone or mixed with all our colours for decoration.
In porcelain painting, usually you must not mix the reds with others colours particularly with yellow, white or pale colours,... except the "mixing yellow" with the reds for decoration ! However, do not add more than 80% of yellow in the reds, this can make disappear the red.
And do not forget that the colours of decoration must be fired from 750 to 800°C maximum.