Just a suggestion, read the rules before posting a new thread. Questions like that one have been asked many many times so you can use the search engine to find it. You will get eaten alive by some of the people that have been here much longer than myself. Trust me I know, I have got my head chewed off a few times for asking similar questions. Learn from my mistakes.
You need to have your image hosted on a webserver somewhere - (Do not use an image hosted on someone elses webserver - it is very very rude, and it crashed my wiki server last month.) You can get free image hosting from www.photobucket.com among others. Once you do that, you simply add [ img ] image_url [ /img ] (without the spaces...) to your post and the image will show up. Hope that helps.