do you mean the merge cells function? if so then i am sorry to inform that it is not available in iworks for ipad suite.
If you mean where when entering text it overlaps other cells, it is controlled by the wrap text in cell function.
select the cell containing the text > press the i icon > go to the cells tab > enable wrap text in cell function.
if its off then the text you enter will resize the cell according to the length of the text entered!