Illuminare is a verb ending on -are. It follows the first verb conjugation, like amare.
If you want to address one person, use illumina. If you want to address multiple persons, use illuminate (the plural version).
Imperatives usually (not always) come at the beginning of the utterance.
I think animus should be in the accusative case, because it is a direct object. Thus it should be animum.
Meus (-a, -um) is a possessive pronoun. It is declined as an adjective of the first and second declension. So it should be meum.
I think the translation should be: illumina animum meum.
The word choice seems right to me.
According to my dictionary, animus (-i) can be translated as: soul, spirit, memory, will, pleasure, heart, character, mood, bravery, thorn.