Multiple Flat Rates

Hi Guyzz,
I need to implement multiple flat rates in ma shopping cart for customers.
Something like this:
Standard: $7
2-day: $14
Overnight: $21
But what we have currently in our opencart is single flat rate option .. For this we need to do code in admin panel i guess. Since am new to opencart, i'm finding very difficult to proceed. Cud anyone plz help me in doing this????
If u give me the code, i will be very happy as i'll learn from it and implement it..
Tanx in advance

search Multiple Flat Rates as this has been covered over 100 times