Increase sharpness in areas of your image

Select the Sharpen Tool from the toolbar. If you can’t find the Sharpen Tool, click and hold the Blur Tool to show the other related tools, and then select the Sharpen Tool.

From the Brush Settings menu, choose a Brush tip and select options for the blending mode and strength value.

Select Sample All Layers to sharpen using data from all visible layers. If this is deselected, the tool uses data from only the active layer.

Click on Protect Details option to enhance the sharpening effect on the image and minimize artifacts. In case you leave this option unselected, the sharpening effect on the image will be more pronounced. 

Drag it over the part of image that you want to sharpen.