Packing UVs in different UV squares

 Open the "layout" option box in the UV editor (modify->layout)

Adjust the settings as you'd like but to pack in this way you need to check the "Shell Distribution drop down and set it to '"shell centers"

    -Without this the UVs would be distributed along the way to the specified UV square and not contained in it

Change the "Tiles" boxes underneath it to the square you want the UVs in

    -"U" is horizontal while "V" is vertical