Perform the task specified in order to unlock that poster. You can then see the things you already have by using My Cup's Rewards Option.

Effect - Code
Goleo Poster 1 - Complete the Possession Skill Challenge
Goleo Poster 10 - Complete the South America zone in Global Challenge
Goleo Poster 11 - Complete the Trivia Challenge on easy mode
Goleo Poster 12 - Complete the Trivia Challenge on hard mode
Goleo Poster 2 - Complete the Corner Skill Challenge
Goleo Poster 3 - Complete the Free Kick Skill Challenge
Goleo Poster 4 - Complete the Penalty Shootout Skill Challenge
Goleo Poster 5 - Complete the Oceania zone in Global Challenge
Goleo Poster 6 - Complete the Asia zone in Global Challenge
Goleo Poster 7 - Complete the Europe zone in Global Challenge
Goleo Poster 8 - Complete the Africa zone in Global Challenge
Goleo Poster 9 - Complete the North America zone in Global Challenge