If you have everything placed, go to the magnet in your playlist. The magnet means snap to grid, depending on how short your clips are you want to pick the correct length of the pattern. For example, if all your clips are a 4 bars long you want to go to the magnet, click bars, then press shift+Q ( to quick quantize start times). This would align everything up perfectly. If you want only certain tracks to be corrected, highlight them first by holding Ctrl+Left-click and dragging your mouse over the notes. Hopefully this helped.