There's a few ways you can do this. One is to add a "Layout" (click "Add To Main", choose "Add Layout" from the popup menu, set it to 2 columns by 1 row). Now you have 2 columns and you can add a different image block in each one.

Another approach which might work is adding a "Content" block, and inserting images into that -- you might be able to align one to the left and the other to the right using the text align toolbar buttons.