Albert Barnes Commentary 1 Kings 3:7

"And now, O Jehovah my God, thou hast made thy servant king instead of David my father: and I am but a little child; I know not how to go out or come in." — 1 Kings 3:7 (ASV)

See the note on 1 Kings 2:2, and regarding the hyperbole in the phrase “little child,” compare Genesis 43:8 and Exodus 33:11.

How to go out or come in - This expression is proverbial for the active conduct of affairs (see the cross-reference).