First of all, you have to open up Photoshop on your PC. You can double-click its icon on your desktop, or you can find it in the list of programmes after pressing the start button.
After opening up Photoshop, you have to find the picture which you want to edit. Click on the ‘File’ option given at the top left corner of your screen and click ‘Open’. Then, select the picture by clicking on it and click on the 'open' button. You can also open the picture by double-clicking on it.
Use the zoom in tool and bring the lip area into focus. After that, select the ‘Brush’ tool. You have to use the soft-edged brush, set to a size that is smaller than the lips. Now, select 100% black colour and create a new layer on your image, otherwise the changes will be made to the original file. Then, click ‘Q’, to open Quick Mask mode.
Before you can start painting, you have to select the relevant area, i.e. the lips. The paint area (lips) will be shown in translucent red colour. Then, click ‘Q’ once again in order to Leave Quick Mask mode. You will see the selection marquee surrounding the lip area.
Select the ‘Solid Colour’ option and choose the desired colour which you want to paint the lips with. After applying the colour, you have to reduce its opacity in order to make it more transparent. It will make the lipstick effect more realistic and natural.
Pick the ‘Eraser Tool’ and erase any extra colour from the lip area. Select the ‘File’ option again, and click on ‘Save’ or ‘Save As’ to save your file.