We embody what we believe to be true about God through our works, such as with James 2:18 saying that he would show his faith through his works, so everyone who is a doer of the same works as James believes in Jesus. In other word, the way to believe in God is by embodying His likeness through being a doer of His character traits, For example, by being a doer of good works in obedience to God's law, we are embodying God's goodness, which is why our good works bring glory to Him (Matthew 5:16), and by embodying God's goodness we are also expressing the belief that God is good. Likewise, the way to believe that God is just is by embodying in His likeness through being a doer of justice, the way to believe that God is compassionate is by being compassionate, the way to believe that God is holy is by being a doer of His instructions for how to be holy as He is holy, and so forth. This is exactly the same as the way to believe in the Son, who is the radiance of God's glory and the exact likeness of His character (Hebrew 1:3), which he embodied through his works by setting a sinless example for us to follow of how to walk in obedience to God's law. This is also why the Bible frequently connects our belief in God with out obedience to Him, such as with Revelation 14:12 where those who kept faith in Jesus are the same as those who kept God's commandments.
In Ephesians 2:8-10, we are new creations in Christ to do good works, so while Paul denied that we can earn our salvation as the result of our works lest anyone should boast, God graciously making us into a doer of good works in obedience to His law is nevertheless still a central part of His gift of salvation.