Games are divided into IC (In Character) and OOC (Out Of Charater) threads. At least in theory. In practice they tend to mingle (at least in my games). Anyway, you need to follow them simultaneusly, and even that does not give you any guarantee
You must understand, that the game is an action-reaction play. Only that while in tabletop game GM reacts on small pieces of action, in play-by-post the players actions have to be larger, more time consuming, otherwise the game would never end. The result of this is that sometime, GM must intervene, end the timeplot gets tangled, in other moments, combats that last few seconds takes weeks RL to accomplish. Some of that combats are taken to the chat tools to speed up, that's why you can see large pieces missing. Same with private messages, that solves many issues, and to the forums only solution is posted so other players (that know the context) understand and accept.
To understand the flow you would have to join a game. There aren't many openings so stay around and post when there will be one.
and most important:
welcome 
