BBCode is something that forums use for allowing very simple html and bracket commands to be used to display things such as images and links for a positive user experience.
To an inexperienced user it can seem like an incredibly daunting task to try and understand exactly how all of this code works, but once you get the hang of it, you will find out it is actually quite simple!
Step One: Adding a Link
For a clickable link, use this code and replace the part after 'url=' with your own url:
[url=https://www.example.com]My Awesome Text![/url]
So, if you were trying to link to google.com you would put:
The part that just says 'Google' inside the two tags is your placeholder text, so you can make it say anything you want. The final result would be: Google
Step 2: Displaying an Image
For an image, use the following code and replace the URL for the Image. For Kboards you won't upload images like you would on facebook and twitter. They don't host them, so you need to host an image externally. You can use one on your website or anywhere online: just find an image, right click, copy image address, and then Kboards will find and display that image for you.
Notice how this one doesn't use the 'url=' tag because you are just supplying the URL between the tags.
Telling the link 'height=125' tells the browser to display it as certain size. If you use multiple images, this will help you keep them all consistent.
I wouldn't go higher than 'height=150' for the size because then you're taking up a lot of space for your images and you might get a message from the Kboards moderators that you have a bad signature.
Step 3: Clickable Images
The outside wrapper is the 'url' and that makes it clickable. Then, we just put our image we built inside those tags instead of a word, and voila we have a clickable image. The best way to do this is going to be to use covers and links in conjunction to make a compelling signature.
If you build two images, just put a space between the first and second url tags and it will put them side by side. You can link out to anywhere you want, though if you link directly to Amazon and want to use your Amazon images, you can just use this kboards tool. All you do is supply the ASIN of your books you want to display and they will build the links I showed you how to build for you.
If you have your own Amazon affiliate account, DO NOT include that affiliate tag on the links that you are embedding into your Kboards signature. Use the Kboards tool. Since you don't own their forum and are not affiliated with it, Amazon will close your account if/when they find out your links are on sites they shouldn't be.
Your affiliate account is for your listed websites that you own (and social media associated accounts). If this is your situation and you still want affiliate traffic and backlinks, then you should be linking your signature your own website which CAN have affiliate tags, not Amazon. Then, readers can browse and click through to Amazon the way they are supposed to.
Some people feel that you should only use your signature to link to Amazon on behalf of kboards (since they run affiliate links and it can help make them money) and they will tell you about it, but it isn't required. For me, I advertise and promote with kboards (to little effect, which I know up front) which I consider to be more than adequate compensation to keep the board alive.