Setting header and footer margins in Excel is a two-step process. First, you need to set the top and bottom margins for the header and footer, respectively. To do this, go to File > Page Setup. In the Margins tab, enter the desired margin values in the Top and Bottom text boxes. Then, click OK.

Next, you need to set the left and right margins for the header and footer. To do this, go to File > Page Setup. In the Margins tab, enter the desired margin values in the Left and Right text boxes. Then, click OK.