Hi and welcome

The Sigs and avatars can be configured in the 'My Home' page. To upload a picture as part of your text, simply type your text and click on preview reply (left). Then press continue and you will be forwarded to another page. In this page, click on where the image should go and then click on 'Image' below the text box(next to smileys). A dialog box will ask you for a direct link to your picture.

If you need to upload the picture on some image hosting servers try photobucket or imageshack.

Hope this helps