Click on the "Browse" button and you will find your files on your computer. Look in the folder you have the picture in, then hit host it! and the next page will show your image uploaded and hosted online.
All you need to do then is to copy and paste the url for the photo from the bottom link that they show you and put it in the "img" tags on this site if you want to share it here.
This site has a good faq about posting photos if you look through the help topics.