Où = when, where (in the context of a relative clause, however, où can be translated as "that").

Jour de fête = holiday

Tu t'amuses = Second person singular, present tense indicative, of s'amuser, "to have fun."

L'endroit = the place

Tu te sens = Second person singular, present tense indicative of "se sentir, "to feel."

le plus libre, la plus libre = the most free.