Select the range of cells you want to shade
Go to the Home tab
Click Conditional Formatting
Select New Rule
Choose Use a formula to determine which cells to format
Enter a formula such as `=MOD(ROW(),2)=0` for even rows or `=MOD(ROW(),2)=1` for odd rows
Click Format
Go to the Fill tab
Choose a shading color
Click OK
Click OK again
If needed, adjust the formula to match the first row of your selected range
To apply to a table, select the table and use Table Design
Check Banded Rows in the Table Style Options