。
She told her son to behave well at home.
Literal
She [topic-は] son [to-に] home [at-で] manners-well do [so-as-ように-と] said.
~ように言う is the indirect-command pattern — 'tell X to do Y.' The ように nominalizes the desired action; the と is the quotative, marking the content of speech; 言う is 'say.' 行儀よくする ('behave well, mind one's manners') is built from 行儀 ('manners, behavior') + 良く (adverbial of 良い) + する. 行儀 is a culturally weighty word — Japanese childhood includes a great deal of explicit instruction in 行儀, from chopstick-handling to bowing.