As mentioned by Shadow 10 Years Wizard, if your image is over 2 MB, you can upload it directly to image sharing websites, then include a link in your post.
Here's a detailed explanation of the steps if you're unsure how to do so:
PC option - Using Imgur:
Note: It is difficult to upload to imgur quickly on a smartphone (unless you want to install their app)
- Go to https://imgur.com/upload (Only works on a PC, not a smartphone)
- Drag your image into the page, or click Choose Photo/Video to look up its location on your device. You could also paste the image onto the page.
- Wait for it to upload. There may be an advertisement you have to wait for\close. And very large images may take a while as well. If so you may see an uploading window like this.
- Copy the link. You can just select and copy the page address at the top, and it'll give a smaller version. Or you should be able to get a link directly to the image by moving your mouse over the image and selecting the copy link button that pops up.
- Paste it into your StackExchange post and rejoice!
You can upload up to 20 MB images, as well as animated GIFS\videos up to 200 MB.
Smartphone option (or for any device) - PostImages:
- Go to https://postimages.org
- Drag your image into the page, or click Choose Image (if prompted for an action on Android choose My Files to be able to navigate to your file)
- Copy the direct link. On smartphones you may need to scroll down below the image to find this link. You can use the copy button on the right of the address, or select and copy it yourself.
- Paste the link into your StackExchange post and rejoice!
PostImages max image size is 24 Mb, which should be plenty for almost all images, other than the most extreme resolutions of smartphone or DSLR cameras.
Hopefully this helps users lacking experience to upload images in their posts and improve site usage.