Not FaceBook, you do need to think about what you post here. Warren is being very kind and explaining how to post, and it is a very polite explanation, very common and pretty much the same across all forums that run SMF to do the blog side. the Captha is a simple way to reduce spam, it goes away after a certain number of posts when the SMF software starts to think you are a human and not an automated spam script.
The basic option is to click the attachments, add the image via selecting it in the dropdown menu, selecting the next one etc until you have them all or have reached the limit, then click post. You can also choose to return to the post or get notified about replies as well there. It seems to work well for the rest of us, you can even paste a video URL into the text box and it will be automatically made into a link.