I think I made small errors at each stage of this, typing the wrong name or picking the wrong file, and of course getting nothing or a bad file as a result. So I kept at it until I got it right.

First thing, of course, was to make sure bspatch was installed in a directory in the path, so that I could execute it from the directory where the patch and image files were located.

Because I knew I had messed up earlier, I redownloaded the patch file, just in case.

I unzipped the Nokia firmware image.

Then I opened a command window and navigated to the directory with the firmware and patch files.

I entered the command (I won't use the full file names since they're so long):

bspatch Nokia-image-51-13.bin a-new-name-for-the-result.bin the-patch-file-51-13.bin.bsdiff

Note that there are 4 parts:
- bspatch
- the firmware image name ending in bin
- a name for the resulting patched image
- the patch file ending in bsdiff

If you're doing all that and don't get a result in under a minute, I don't know what's going wrong.

Good luck!

Roger