To add a border in Photoshop CC, follow these steps:
1. Open the image you want to add a border to.
2. Choose "Select" > "All" or press Ctrl+A (Windows) or Command+A (Mac) to select the entire image.
3. Choose "Edit" > "Stroke" or press Alt+Backspace (Windows) or Option+Delete (Mac) to open the Stroke dialog box.
4. In the Stroke dialog box, set the following options:
• Width: This is the thickness of the border. Enter a value in pixels.
• Color: This is the color of the border. Choose a color from the color picker or use the eyedropper tool to select a color from the image.
• Location: This determines whether the stroke is added inside, outside, or centered on the selection. Choose an option from the drop-down list.
5. Click "OK" to apply the stroke.
6. If the stroke is too thin or too thick, choose "Edit" > "Undo Stroke" and adjust the width value in the Stroke dialog box before applying the stroke again.
7. If you want to adjust the position of the stroke, use the Move tool (shortcut key V) to move the image within the border.
8. Once you're happy with the border, save the image.
That's it! You've successfully added a border to an image in Photoshop CC.