As the description reads, score 100 goals over all the games you play. All modes count, difficulty doesn't matter.
If you want to check on your progress you can look at the leaderboards, and go over to "Most Goals". That number is how close you are to this achievement.
In terms of tips for scoring, I've found 1-timers (pass to an open player and shoot immediately) to be the most effective. Maybe it's just me but I'm definitely finding the more I play the game the harder its getting to score (I think the game auto-adjusts the difficulty depending on how well you're playing). This video has some tips as well:
You'll get this well before 100 Wins (by definition, you must've scored at least 100 goals if you've won 100 games).