Smaller is more accurate but slower. Use about 1/100 of the fastest period in your circuit.
Tips
Drag a part from the left onto the grid, or click it then click the grid. Press R to rotate it first.
Drag from any pin to another to wire them; wires bend at right angles. Hover a pin to see its name and voltage.
Drag a box on empty grid to select several parts. Right-click a part for more actions.
Right-drag to pan, scroll to zoom. Switch to Realistic view in the toolbar to see real parts.