To change the size of a column, place your mouse pointer on the line that divides the column letters at the top of the column you want to change.

If you wanted to change the size of column F, place your mouse pointer on the line separating F and G. Your mouse pointer will turn into a vertical line with a small arrow on either side. When you see this pointer you can change the column size by holding the left mouse button and dragging the column edge to the left or right.

Now the size of column F has been changed.

To change the size of a row, place your pointer on the line separating the row numbers at the left of the worksheet. When you see the pointer with a vertical line and an arrow on either side, drag the edge of the row to change the size.

In this instance, the size of row 6 has been changed by dragging the column edge between the numbers 6 and 7, downward.

You can also change the size of rows or columns by using Format->Row->Height or Format-> Column->width from the menu bar. This will display a box that you can use to specify a row height or a column width.

(Changing the value in this box will change the height of the selected rows)