It’s fairly easy to blend two images in GIMP. All you have to do is: Open the two Images in GIMP. Blend the images using layer opacity/blend mode/layer mask. Export the resultant image as JPEG/PNG.

When it comes to knowing how to resize an image with GIMP, a basic resize is an easy process, as you'd hope. Open up your image in GIMP, click on "Image" along the top menu, then select "Scale Image" ...