If you're just changing the width/height you can do that by clicking on Format then row or column and change it. If you want to adjust width/height on a specific row or column, click on that row/column header and find where it says column width and adjust it. If you want the entire spreadsheet to fit to the cells in each column click on the furthest column/row header which is usually to the left of A and above 1 and it will highlight the entire sheet then move your mouse over to a line between columns and you'll see a two lines crossed, double click, it will auto adjust the columns, then do the same thing to the rows.
I just checked on one of my spreadsheets that has figures in it and I added a column and it adjusted the figures to the new column name itself. I clicked on the column heading and it highlighted the entire column and then I highlighted "insert" and it inserted a new column.
