You need to upload your pics to a site like photobucket first.
http://photobucket.com/
Once you've done that, all you do is copy the IMG code & paste it into your post on here. Same thing for your siggy pic.
ETA: You might have to reduce the size of some of your pics BEFORE you post them. Most of my pics are around 2.5MB which can take ages to load especially for those with dial up & they look H-U-G-E. I reduce mine to 640x480 before I upload them to photobucket.