It's easiest to have WYSIWYG on for this type of thing until you learn how to code (or fill in code) without it
To put images in your bio (regardless if WYSIWYG is on or not) using a computer rather than a mobile phone is the best way to do it as you need to put in the image address into the area you fill in to place an image, since you cannot just copy an image to put it in
Edit: there's a video on YouTube (here) that can explain a few things to newer users of the site, I'd recommend watching it