To select a field just click it and it's border will turn color.
To see the field's properties just double click it, or select the field and click the Edit Field button.
When two fields overlap you can bring the selected field forward with Bring to Front or push it back with Send to Back.
Once you select a field, you can move it 1 pixel at a time using the any of the four arrow keys on your keyboard.
Normally you can move any field to 1 pixel resolution. But if you want to snap the position of a field to a grid location, click on the toggle Snap to Grid button. If you want to change the grid size click on the edit icon inside that button.