Structure
During the first session, you'll create characters together and introduce them to each other. As you do so, you'll create your group's specific version of Stonetop. You'll also roll some dice to find out what the first season of play holds.
After the first session, the GM will spend a few hours organizing their notes and preparing an initial adventure.
In subsequent sessions, the GM will set scenes and the players will portray their characters. In the first of these sessions, you'll start in the village of Stonetop and establish a little bit of normal life. The GM will then introduce a threat or opportunity, which will prompt the PCs to undertake an expedition.
The expedition will take one or more sessions to resolve. When the PCs have met their goals, or failed to do so, they'll return home. You'll explore how the village reacts to their return (and their success or failure), and how the PCs settle back into normal life.
If your group keeps playing, then future sessions will skip forward a bit in time. The game will help you identify the next interesting situation—the next challenge, crisis, or opportunity that needs to be dealt with in play. The situation will likely lead to another expedition, which again will take one or more sessions to resolve.
Between sessions, the GM will likely want to spend 1-2 hours updating their notes and preparing for the next session. Players will occasionally need to select new options for their characters, or think about what they want to do next, or answer the GM's questions.
Eventually, your group will decide to stop playing. If interest wanes or real life interferes, the game might just fizzle out—and that's okay. But hopefully, you'll be able to bring your game to a satisfying conclusion. See Ending your game for advice on this.