To complete one of the Bullseye challenges, you'll need to hit a weak spot on an object while you're collecting materials from it. To achieve this, you will therefore have to start collecting materials, and from the second hit on an object, hit the target that appears.
For this challenge, you will not have much to do, except approach any object to collect materials there. You will therefore have to give the object a first blow, before finally focusing on its weak points which appear. The game is very generous, and each weak point remains for several seconds on the screen. You will therefore have no trouble, taking your time, to succeed in hitting 5 in a row for the Prestige mode of this challenge.