My computer has microsoft digital that I use to downsize. My newer net book can use paint to downsize pictures. Should be something on your computer to downsize pictures To place a picture in a thread you go to your gallery and pull up a picture and at the bottom is a URL. You need to copy that and then paste in in a thread. A lot of work for posting pictures.
I use MS Paint for my downsizing tasks. I open the pictures in Paint, hit "CTRL W" and change the Horizontal and Vertical % to 50. I then hit "CTRL W" a 2nd time and downsize it by either another 50% or 75% depending upon how big the pic was originally. Then I save it as a new file usually by adding the letters "ds" to the file name thus keeping my original. The "ds" files are then uploaded to the appropriate album.
It works very well for me and only takes a few clicks to downsize a photo.
I use a program called paint.net to resize. It was a free download. Open the picture go to image, resize, set the number of pixels for the horizontal (I use 800) the vertical automatically changes to maintain the aspect ratio, save with a new name then upload to the forum. It is the easiest I have found for resizing pictures, only 3 clicks and type 3 digits then save.
Unless I am going to resize a full folder's worth of files all at once, then I use PixResizer. The single BEST FEATURE of this program is you can select any size you want in a heart beat with a slide rule, no jockeying around trying to find the single best fit for something.
both are free to use downloads that don't nag you.
I use Paint a lot, but not for resizing, I use it save Screen Captures to a folder.
ALT-PrtScrn to capture the current view.
Paint to paste it into, and then use the Cropping Tool to select only the area I want to save.
Control-N to get a fresh background, and Control-V to paste in the smaller selected area and the save it to disk.