It depends on your pool’s deadline settings.
If the deadline is set to the first game of the week, then the entire pick sheet locks when that first game (e.g., a Thursday game) kicks off.
If the deadline is set to Sunday at 1:00 PM ET, members must submit picks for any early games (like Thursday or early Sunday morning matchups) before their scheduled kickoff, but they can continue making picks or changes for later games up until Sunday at 1:00 PM ET.
Note: Early Sunday morning games are treated just like Thursday games under this setting—picks must be in before kickoff, and changes to those games cannot be made afterward.