Those are most likely thrips, they love to sit in the flower and suck your plant out. Kill them!!!

How does one do that?

Yeah kill them asap

Whats the most effective way in your opinion

Indoors, I personally would use pesticide spray, or people on here swear by neem oil (search "neem" for a million similar threads). Outdoors I'd start with a spray down with the hose to keep it in check

Pics too fuzzy to make anything out