I got this achievement at the end of my second season. I found that you'll generally get two press conferences per Grand Slam event (before finals and after finals, provided you win LOL). So that's 8 per season right there. You'll also get one when you get to 50 wins (near end of first season) and 100 wins (near end of second season). Then you'll get a press conference for any charity event you win. So you ultimately need to play (and win) 8-9 charity events total over those two seasons.