Grid arrangement options are available after adding a composite frame and setting its query on the Editor's Layout tab.
Click on the > button to expand the options:
Horizontal Alignment sets where the grid is positioned on a left-right axis. Choose to left-flush, center or right-flush your grid within the composite frame.
Vertical Alignment sets where the grid is positioned on a top-bottom axis. Choose to top-flush, center or bottom-flush your grid within the composite frame.
Last row alignment sets special rules for the last row of your grid. This is most easily seen when you have an incomplete row of portraits at the end of the grid.
Choose to left-flush, center or right-flush the last row.
