To help you align elements on your sheet, you can opt to view the grid or snap objects to the grid from the Properties bar below the sheet. Press "View" to view this option:
To view the grid, press "Grid." To snap objects to the grid, click "Snap to grid."
Information on using the grid on Editor versions before 6/27/18: https://support.cacoo.com/hc/en-us/articles/212778448-The-Editor