Press Tab to open Companion, see rulers and add Guides to help you align elements.
Drag on the sides to create Guides in either the X or Y axis.
Tab - Toggles the Companion
1 - Toggle XY at Mouse Display
Shift- Hold to move in 32px Increments (1 Flowlab block)
Ctrl - Hold to move in 16px Increments
R - Toggle Guides & Rulers