Select the Clone Stamp Tool from the toolbar
Choose a brush size and hardness in the options bar
Set the opacity and flow if needed
Hold Alt on Windows or Option on Mac and click the source area to sample
Move the cursor to the area you want to paint over
Click or drag to clone the sampled pixels onto the target area
Resample from different areas as needed to match texture and lighting
Adjust brush settings for smoother blending
Use a new layer for non-destructive editing if desired
Zoom in for precise cloning
Save your work regularly