पित्रा by father, मनुजेन्द्रेण by the king, स्वयम् on his own, प्रचोदितः having been ordered, तव your, प्रियकामार्थम् for the sake of (your) pleasure, प्रतिज्ञाम् promise, अनुपालयन् to keep up, किं पुन: needless to say.
In order to keep the promise I shall do everything to fulfil your desire. Needless to say that my father has ordered this.