Welcome aboard. There is a blank line just above the text box that says "Attachment:" to the left and "Browse..." to the right. If you click on Browse, it will open a window to your hard drive. Simply select the picture (typically in the JPEG or ".jpg" file format) and click on it. It will automatically upload the photo from your hard drive to the Web page.
Important note... be sure the picture name does not contain any space or symbols, only letters and numbers. This Web site does not like file names with blanks in it.
I've attached a photo I took of the Grand Princess at St. Thomas last year.
Hope this helps.