If you look on the computer box there should be a slot on it if it is a fairly new computer, put the SD card into the slot, then go to My Computer and search for the SD card on it, you can find it in Mass Storage Devises section of My Computer. Open that and look for the immages, then copy and paste them to My Documents or My Pictures.
Ohh OK. Once you get the pictures on the computer, go to a photo hosting website such as photobucket.com, register an account and upload the immage(s) you want, wait for that to finish. Once it is finished scroll over the immage you want, and a box will pop up with some options, you want the BB or Forums option, click on the link and it will automaticly copy, then go onto the forums, click on your user profile, then click on the more options button near the top of the page, then scroll down untill you find Edit Signature, paste the copyed url there and vollia!