Since you seem to be new or not well versed in photo sharing concepts,
Download to your computer means to copy pictures from somewhere else, whether it's the internet, a flash drive, or a portable hard drive, TO your computer.
Sharing pictures that are already on your computer, would require you to upload them from your computer to wherever it is that you want to share them.
On a photo hosting site, such as Photobucket that Splke mentioned, you upload your pictures from your computer to their site. Then under each picture there you will see an address. If you copy and paste that address into a post here the readers of the post will see your pictures. Uploading to photobucket is as easy as dragging a picture file from your computer and dropping it onto a photobucket "box". Photobucket is free within limits.
Alternatively you can drag files from your computer to the "drag files here to attach" box when you're posting here. But that results in a small thumbnail picture in your post that readers have to click on in order to view the full size picture.
Last edited by vtox; 02-17-2017 at 11:26 PM.