Excel 2007 : adding more rows/info and keeping formulas

New to excel. Using 07. I have completed an inventory and profit sheet using several formulas which work both horizontally and vertically. I now need to add many more rows of info. How do I do this and keep the formulas in place?
Thanks.

right click on the cell (where you want to add rows or colomns) and click on insert and choose entire row or entire column - push ok