Open the image in Photoshop
Select the layer you want to scale
Press Ctrl+T on Windows or Command+T on Mac
Drag a corner handle to resize the image
Hold Shift if needed to keep proportions, depending on your Photoshop version
Press Enter or Return to apply the transformation
Use Image > Image Size to scale the entire image by exact dimensions
Enter the desired width and height
Choose the resampling method if needed
Click OK to confirm changes