First let me say that this is not my specialty, but it's what works for me.
I go here:
Resize Images online
Then click on "resize" on the left.
Then go down under "resize images" and click "browse."
The file upload page should come up.
Click on "pictures" on the left.
Double click on the pic (name) of your choice.
Then the file upload screen will disappear.
Then click on 600 pixels in the "resize images box.
Then click resize.
When it's done resizing, click "download this picture now."
Now you're done with that part and I am sure there has got to be a way to do it faster.
To upload to YT after doing that, go to "attach files" after starting a thread.
Then click "browse" (I think).
The file box should come up.
Click "downloads" on the left.
Pick you pic and double click.
Upload pic.
This part is really easy. I find it much better than fighting with a PC.
That used to frustrate me so much.