You can use rulers and guidelines to accurately place layers, text, and objects.
To Turn on Rulers:
In Edit mode, choose View | Rulers or press Ctrl + T.
To Customize Ruler Units of Measure:
Right-click a ruler and choose a new unit of measure from the context menu.
To Draw Guidelines:
With Rulers enabled, click a ruler and drag the guideline to your desired location on the image.
You can move guidelines you have already placed by enabling the Move tool.
To Enable Snapping to Guidelines:
You can snap layers, objects, and text layers to guidelines for precise positioning. When snapping is enabled, you can move the edge of a layer near a guideline and it will snap to the guideline.
Choose View | Snap to Guidelines or press Ctrl + Shift + G. You can use this keyboard shortcut to enable or disable snapping.
To Remove Guidelines:
Choose View | Clear all Guidelines or press Ctrl + Shift + ;.
To Lock Guidelines in Place:
Choose View | Lock Guidelines or press Ctrl + Alt + ;.
To Hide Guidelines:
Choose View | Hide Guidelines or press Ctrl + ;. You can use this keyboard shortcut to hide or show guidelines.
You can customize the Rulers and Guidelines options. See Setting the Rulers and Guidelines Options.