I finally figured out how to post large size pics! Hope these instructions help you.
Sign up for Imgur (free).
https://imgur.com They want an email address (And a cell phone number in order to send a confirmation number text.) Once you receive and enter the confirmation number into Imgur, you are registered.
Sign into Imgur if you aren't automatically signed in with registering.
Add images to Imgur: In Imgur, click on the green "Add images" button at the top right. A pop up window appears. In the pop up window, you can either browse to an image folder on your computer OR open a second window (on your desktop) with your images and drag them onto this pop up window.
Copy a link: After successfully uploading, a thumbnail of your image appears on the Imgur screen. Click on the thumbnail and a window like this will appear:
You can see a list of links which you can copy. You want the Direct Link. Click on the blue "Copy" button next to Direct Link.
Paste the link: Back at the Wild Guzzi site: Start a new topic or reply. Move your cursor to where in the text you want to place your photo and click on the "Insert Image" icon. See the red arrow below. That's the "Mona Lisa" button, though on my laptop it's hard to tell what that tiny icon is, even with my reading glasses.
In the text box, you will see [img| |img] appear with the blinking cursor in the center. Now paste your image with a (Ctrl-V). Click on preview and you should see your image in all it's glory!