Posting on this board consists of two parts: 1) you must have already posted 10 times; 2) you must store your images someplace on the Internet that allows linking; 3) you must copy or type in the Internet address to the image into a special format in your message.
1) You have already posted enough messages, so you are set on this item
2) Find a place to upload your images such as Photobucket, Smugmug, or some other image upload sites. Note that some are free and some cost. Usually the free ones have ceratin limitations while sites that are not free may have more features. For now, I'd start out on one of the free sites to get used to it. Others on this site use various servces and can contribute their favorites if the wish. Follow the instructions on your site of choice to upload your image(s). Note that you should limit the size of your images to 800 pixels on the longest side to ensure they show up properly on the Disboards. You may be able to set this size at the time you upload your image or you may have to do it in an image editing software application. It's also a good idea to set the uploaded image resolution to 72 pixels per inch. This helps reduce the size of the file to upload. If you have to do this using a software application, ensure you save it out as a copy of the original. Do not save out the file and overwrite the original. You'll find out why later, after reviewing many of the threads here on the DIS.
3) To post and image, most of the sites referred to in item 2 above will provide a string of text characters that describe the link to your image. Some of these text strings include the formatting instructions and some do not. For the ones that do, such as Photobucket, you just highlight that string of text and copy it to a message in the Disboards. For those that do not, copy the text as above, return to your message on the Disboards, click on the icon to Insert Image, then paste the text in the dialog that appears. Ensure you do not end up with two http:// headers in the text you just pasted, then click OK. Use the Preview Post button to ensure everything is correct, then Submit the post.
This may seem long and overwhelming, but it really is quite easy once you do it once (an this is the short version). Don't be afraid to make a mistake when trying this. Most of us have run into issues trying this the first time but people here will help you as you run into issues.