How did Jesus display the power by which He was declared the Son of God?
He displayed the power by which He was declared the Son of God through His miracles during His three years of earthly ministry, one miracle after another. Some miracles more explicitly revealed His power over nature, such as the Sea of Galilee storm when the frightened disciples woke Him.
Les explains that verse 4 says Jesus was declared to be the Son of God with power. He manifested that power in all His miracles throughout the three years of earthly ministry, one miracle after another. Some miracles were more explicit demonstrations of His power over nature than others. For example, while they were in a little boat on the Sea of Galilee and a storm was raging, the disciples were scared to death. Jesus was likely below deck sleeping in a little double-deck boat. The twelve woke Him and let Him know how worried they were.