Assuming you have a windows computer...
1. Open your image "filename" with windows paint.
Great advice, and Microsoft Paint was installed on virtually every Windows PC, so there's no need to download other programs!
2. Use "skew" to get width of image to around 1000 pixels. You will have to experiment with this value to get the reduction you want, just keep both numbers equal.
3. Save as "filename-sm.jpg" if you want to keep large file original.
Then just upload...
2: Actually, we want to use "resize" (also known as "stretch" in some older Paint versions) or the top two boxes that you used in your example -- the "skew" boxes at the bottom will change the SHAPE of the picture.
I'm not sure what Windows or Paint version it started with, but some newer versions automatically default to "keep both numbers equal" via a checkbox marked "Maintain aspect ratio." (If you change Horizontal to 50, Vertical will instantly change to 50 as well.)
And as shown in my picture, some newer versions also allow us to click the button for "pixels" instead of the one for "percentage" and resize a picture to an exact size on the first try!
3: After doing this to a few hundred pictures over the years, I've learned to change the order of these steps to "1, 3, 2" -- open the file, immediately "save as" the new filename so I don't accidentally mess up the original picture, and THEN make my changes.
Good on ya. I have not successfully uploaded a pic on this site yet, after many many tries, so I think my photo posting days are done here. I'm just a commenter now.
I'm curious as to what's happening (or NOT happening) when you try to upload a pic here -- the biggest problem that I'VE found with this forum's "upload" feature is the additional and somewhat annoying "insert" window that pops up below the text window:
It's an an extra step that's not needed when uploading pictures to any other forums I belong to -- but if you don't click "thumbnail" or "full image" -- or FORGET to click, as I often do -- I've had trouble getting the picture to appear.
Sometimes the picture doesn't show in the "post preview" except as text saying "attachment_____" but it looks fine in the post itself.