To successfully insert images in forum posts, ensure the image link includes a proper file extension like .jpg or .png. Users can attach images directly to their posts, which will appear in an "Attached Thumbnails" section. After uploading, it's recommended to preview the post to check the attachment. Additionally, copying the link from the separate window where the image opens can simplify the process. It's important to keep image sizes around 800 pixels in width to maintain proper formatting on the forum.