You can probably find software on the net to convert BMP to JPG. If you adobe photoshop, just save it as a jpeg. if you dont...
go to google.
do a search on "freeware bmp jpg convert"
do some hunting and download one until it works the way you want it.
follow king lizard's step-by-step instructions to upload the picture
once uploaded, copy the URL (the link) that comes up on that page that says "your file has been uploaded under the filename
www.abovetopsecret.com..."