You need to get the grand kids in to show you how to use it.
I'm the same with mobile phones, I got one a year ago and still can't use it
But as Jacky says, take a break from the site and try again later. Underneath the window where you type stuff are 2 buttons. One button has "Post Quick Reply", the other button has "Go Advanced". Click Go Advanced.
In the Advanced section a window will appear where you type stuff. Just above that there are little buttons. Fonts, Sizes, A (colors), Smilies (smiley face). On the right of that is a button that looks like it has a paperclip on it called "Attachments". Click Attachments and a smaller window should open up and have "Upload File from your Computer". Under that are some buttons called Choose File.
When you click Choose File, you should be able to look in your computer's filing system and add the image you want to add. Then upload.
Hope that helps, if not, call the grand kids over