Any website that allows posting will have a button that says "post" or "upload Image" or something to that effect. You probably have to register to do this. When you click the "post" button, you'll geta dialogue box that will have a "browse" button. Click this to go to the drive and folder where your picture is stored on you computer. Choose the image you want to post and double click it or highlight it and click an upload type button. You may now have a box allowoing you to put caption or other information relating to your picture. You'll now have to press a button to Finish" or "process". Your picture is on the web.
To reference that picture here, go to the site where the picture is. Right click the full size image and a box comes up. Click properties and choose the Address, just as you did in posting your Hogan's Heroes pic in your signature. Past eh full addressin the body of your text and your picture is posted here.
A good, simple site for posting model pictures is www.armorama.com Once registered, you can post pictures by clickin "My Gallery" on any post you've put in a thread as well as from the "my Account" page.