Upload your picture to a hosting website (I used TinyPic) and just grab the code for forums and insert into your sig. But you need to post 30 messages before you can have access to your sig.
youtube is a tool in design be creative and learn abit more the design are not high standards it takes time try seing c4d for text if your a 3d designer if your 2d try keeping text simple use drop shadow and some basic grundge overlays just keep the designs simple add me on skype if you want learn abit more my skype is waynev633