There are number of online image resizing websites, if you don't mind uploading images to a 3rd party.
The one I tend of direct people to is resizeimage.net, as it's got various simple options, including scaling (4) and compression (7). Once you've chosen the options you can click the "Resize Image" button and it'll display the new resolution and file size, with links to view or download the new image.
Hmm, I'm not understanding the steps on the site, to be honest I don't what the options mean. Scaling,compression, etc which option do I use just to reduce the file size to under the 500 limit on here. I think I am a simple one 🙄
Reducing an image file size tends to require 2 things, reducing the resolution and increasing the compression.
As an example, using a JPEG image that was 1920x2560 in resolution and 1MB, I used the following options:
(4) Resize your image:
I opted for 40%, which gives a reasonable resolution of 768x1024.
(7) Optimize your image:
I tried a couple of options here:
(a) Using the default 'Best quality'
(b) Using 'Normal compression' of 90%
Testing these options resulted in the following file sizes:
4 & 7a = 547KB
4 & 7b = 173KB
You haven't said what file type your images are. By default resizeimage.net will use the same file type for the output image format as the input. However, if your original file types are PNG, BMP or GIF, they won't always compress that well (depending on the image content), so you may want to try changing the output image format (6) to JPG.
EDIT: I just realised you say in your post title you're using JPG images, so ignore the last bit of my comment, regarding the image format.