Since you didn't start with a plan, it is going to take some thinking and a bit more knitting. You can lay the squares out on a large table or on the floor and arrange them in a form that is pleasing to you. It is highly unlikely that you will be able to arrange them so that they all fit together. But once you like where they lie, you will likely have to knit more onto the squares that need it. It might be on one, two, or all four sides.