That's why I gave you the link to all the techie info.
I'm a complete ignoramus about computers, don't know my pixiels from my urls, but I do manage to resize, using paint shop pro.
The page I linked to gives you the instructions for lots of different resizing packages - all you need to do is find the right set of instructions for whatever package you have.
If you do not have a package, you will find out there how to get hold of a free one.
I like paint shop pro, it's the one I have learned, but other folk seem to prefer some others. You just need to decide which package to use and follow the instruction.