Ralph, Jack and Simon were returning from the the mountain-top on whcihthey looked around to see if they were on an island or not. They were busy collecting food on the way back towards the platform. (reference to chapter 1)
As they returned to the platform, where they announce meetings, Ralph blew on the conch to get all the kids' attention
Moments later, all the kids were at the platform for the meeting. Ralph was sittting on a tree trunk and made an announcement confirming that they are on an island.
Jack steped in the announcement and announced that he and the choir boys can hunt for pigs.
Piggy joined the crowd and asked for the conch. As he held the conch, he announced that nobody knows that they are on that island.
Ralph than took the conch and he announced that they should have fun on this islnad, that this is a good island and with food.