You can switch between the files currently being edited by toggling between them, by switching directly to a particular buffer, or by using “point and shoot” selection.
Select FILE > Previous buffer or FILE > Next buffer ( F5 , F6 ). This toggles, “round-robin fashion”, to the next/previous open edit buffer and the file (if any) being edited in it.
or
Select FILE > Buffer switch ( F4 ). You are prompted for the buffer number.