Deus, in adiutórium meum inténde.
Deus (vocative case) = God. We are calling out to God. Hence the common English translation, “O God.”
inténde = imperative (singular). “O God, come / attend / be present!”
adiutórium = help, assistance, in the accusative form, which, when attached to the preposition ‘in’ implies physical or moral motion, thus ‘to’, ‘to my assistance.’
How would you say ‘God came to my assistance?’ = Deus intendit in adiutorium meum.
How would you say ‘O God, come to their assistance?’ = Deus, in adiutorium eorum intende.