Press home (one's) advantage phrase
To gain a further advantage for yourself from a situation in which you are better, stronger, or more successful than your opponent, enemy, etc.
The enemy is now in retreat. Let's press home our advantage and kill them all.
Once realizing that their team was getting weak, we pressed home our advantage and defeated them decisively.
The verb "press" must be conjugated according to its tense.
The origin of this phrase is not clear.
Meaning absolutely certain or without a doubt
I am as sure as God made little green apples that Peter's the one for you, you two make a beautiful couple.