To insert a picture in your blog post you'll need to upload it somewhere (Photobucket, ...) and put the link in this code:
[img] YourLinkHere [/img]
However, if you want to align your image to either side of the screen (with the text going "around" it) you'll need to add this:
[img align=right] YourLinkHere [/img]
Obviously, to align to the left, put "left" instead of "right".
Lastly, if you want to rescale the image to fit your blog post nicely you'll need to add this:
[img align=right width=150] YourLinkHere [/img]
In this case, your image would be 150 pixels wide. Simply change the number if you want your image to be larger or smaller.
Hope that helps.