Hi Kristen, click the Post Reply button. Under the box you type in to respond to a thread there are Smilies and then the Additional Options section.
Click on Manage Attachments, then click Browse, choose the picture you want from your computer, then click Upload.
If the picture isn't small enough you have to resize it or it will not work.
If you can't figure it out, ask again. People are happy to help.
Welcome to YT.
I look forward to seeing Sophia's picture.