Here's how to post thumbnails. First register at an image host like imagebam.com. It's free to register and doing so allows you to create galleries and keep track of your pics. Imagebam.com is used in this tutorial but most image hosts are very similar.
Go to Imagebam.com. Click the 'Select Files' button. You'll get a pop up window. Navigate to the directory the pics are in that you wish to post. Select multiple pics by hitting the control key and left clicking on each pic. You can also click on the first pic, hit the shift key and click on the last photo to select a group of photos. Once you've selected your photos, click on the open button.
The files you selected will appear in the box.
Where it says Select Type: (required), click the drop down box and select 'Family Safe Content'. This will ensure that your photos are marked as family safe and also no porn pop up ads will be shown when viewing your photos.
Click the upload button.
Right click inside the box for BB Code and copy that code.
To post your photos at the forum paste the BB Code inside the reply box here and hit the add reply button.