could you show us pictures? i'm confused as to what you did-vs want to do---do you mean you've created a quilt top without extra spaces? if that is the case- and you want to add between the squares you have sewn together you really have no choice except to (un-sew) and add what you want to where you want.
if you really don't want to take apart what is together but you want to make it larger you could add borders...but pictures may show us some other alternatives