To sit at the "right hand of God" is a symbolic action of receiving great honor and authority from God. AT: "sat in the place of honor beside God" (See: [[rc://en/ta/man/translate/translate-symaction]])
This idiom means they proved that their message was true. AT: "showed that his message, which they were speaking, was true" (See: [[rc://en/ta/man/translate/figs-idiom]])