GIMP is an open source cross-platform image editor that is similar to Adobe Photoshop. The learning curve for GIMP is pretty steep so this post aims to describe how to edit layers of a PSD file. In this example, we assume that we want to add our own image to a mock-up similar to what is shown here.

The steps to follow are:

1. Open the .psd file using GIMP. A dialog toolbox for “Layers-Brushes” will appear. Select the layers tab click on the layer you want to edit.
2. Open the image file, that you want to replace the layer with, using GIMP. At this point GIMP is open twice. Select the replacement image in GIMP and click Ctrl+C to copy it.
3. Return to the GIMP window where the .psd file is open and select the layer to edit. Then paste using Ctrl+V. A new layer called “Floating Selection (Pasted Layer) “should appear. Right click on it and select Scale Layer in the dropdown menu.
4. A new dialog toolbox labeled “Scale Layer” appears. Adjust the numbers for the length and width to the desired levels (unfortunately there is no click and drag function for this).
5. To save the final output, select File Save As and this will save the final output as a .xcf file which will allow you to edit the layers again at a later stage. You can also export the layers to a more convenient format like Jpeg.