How can I align 3 edge detected images

I divided one image into 3 sections and now I have to place the edged detected images b,g over the r

so once I align the 3 images from b,g,r (backward to front) I'm supposed to use color filters to create one colored image

How can I place the images over each other, what method do I need to implement?

the original image was uploaded on matlab then I divided the original image into 3 using matlab functions

so i found the size of the picture, then i divided that picture into 3

so lets say the image variables are

x1, x2, x3

what can I do to align them? what methods, etc do I need and the simplest one if necessary with something to do with the shift function.

so how can i align the pictures from back to front

regards