If you do not have Infranview installed, download it from the Infranview official web site and download.Use default options - just follow the prompts.

When you have Infranview installed, find the folder with your pictures.

Right-click on the image, select the 'Open with' option and left-click on the 'Infranview'

Select the 'Image' menu and then click on the 'Resize/resample'.

Click on the 'Set new size' radio button, type 1024 (or other value if needed) as width and set units to pixels. Then click on the 'OK' button.

Click on the 'Save as' button in the top-left corner of the Infranview window.

Type the name of the file. You probably want to use a different name than the original image. Make sure that the 'Save as type' is set to JPG. Click on the 'Save' button