Those that don't have chronicle sheets available on their product pages/in the Additional Resources are not yet sanctioned for Pathfinder Society play. Some of these may be sanctioned in the future, while others may not. They are for play in home games. Those that do have chronicle sheets can either be played in a home game mode where you play characters by any rule set made by the GM and apply the chronicle to a legal PFS character of that level. Alternatively, just the sanctioned portions can be played with a PFS legal character at the appropriate levels like any other PFS scenario would be played.