This Could Be A Declaration of Faith From The Original Petitioner or From The High Priest (Psalms 20:6).
‘Now know I that YHWH has saved his anointed,
He will answer him from his holy heaven,
With the saving strength of his right hand.'
This could be the continuation of the words of the leading petitioner, or the words of the High Priest. Either way his confidence is that YHWH will save His anointed (the Davidic Prince), delivering him from his foes by answering from His holy heaven with the saving strength of His right hand (by exerting His strongest power) and giving him victory. ‘Has saved' is expressing the certainty that it will be so. Alternately ‘His anointed' may mean the people as a whole.