For your signature, go to your Control Panel found here

Then click on Signature

Next, click on that little icon of a mountain with a red sun!

The tricky bit is getting your pics to a nice handy size. So click on the corner like this:

You might have to fiddle about a bit to get them just right When you're finished, make sure you save or update

To post pics, just select the picture icon above the text box, select the file you want, then click the Add Image box.

To add an Avatar, follow the same steps as for adding a signature but select Avatar instead. Your Avatar will be resized automatically to suit the forum.

If you notice any pics over running the screen,please bring it to my attention in case I missed it and if things aren't working as they should, just ask for help