Conditional formatting to insert symbols

Hi friends,

In the attached file, I want a conditional format that will insert symbols in the cells as follows:

Where the previous month value is higher than the current month (eg Jan higher than Feb), insert red down arrow
Where current month value is higher than previous month value, insert green up arrow
Where the current and previous months values are equal, insert yellow triangle symbol.

I will also appreciate it if the steps are explained to me so that I can handle it myself subsequently.

Thanks.

The symbols will be in the same cells where the values are.