It would be great if people would just post photos of the things they’re selling or giving away, instead of asking people to email them for photos. I guarantee that your thing or things will find a new home much faster, too.
There are a lot of free image hosing sites, and one of the easiest to use is Imgur.
Just go there, click on the blue “Upload images” button at the top left, and drag your images onto the screen, or click “browse your computer” to upload. Then click “Start upload” and wait a moment. When the uploading is done, you get a new URL (up there at the top of your browser window) which you can copy and paste into your post. It really could not be much easier.