find out what your terminal program is called and try reading it's manpage for what options it needs.
for example gnome-terminal can use the following;
Specifies the startup geometry for this terminal. The geometry specifies the desired width and height in terminal characters. For example: --geometry=80x40 will create an eighty-column by forty-line terminal. You can also specify the location of the terminal Window on the screen; for example, --geometry=80x40+100+200 will create a Window whose top left corner is 100 pixels to the right and 200 pixels down from the top left corner of the screen, while --geometry=80x40+100-200 will give a Window whose bottom left corner is 100 pixels to the right and 200 pixels up from the bottom left corner of the screen.
The script would then just be 4 lines, each one opening a terminal with a different geometry