We cannot do your homework for you, but we can give you pointers.
The Conditional Formatting command is on the Home ribbon.
If you want to format the current cell based on values in other cells, you will need a formula to determine which cells to format.
Such a formula needs to return either TRUE or FALSE. This formula returns a number (if the cells contain numbers):
=$A$1+$A$2 -- This formula returns either TRUE or FALSE:
=$A$1>$A$2, depending on which number is greater.
When you build a formula for conditional formatting, you can either type a cell reference or click a cell.
Conditional formatting can be copied to other areas of the spreadsheet, for example from one row down to other rows.
When a formula applies to more than one row of data, you may want to use references that are relative to the current row, so you don't want any $ signs before the row number.