First, you need to know the value of each term's exponents. Then, change their position.. (Sorry can't explain it farther, but here's an example.)
For example, your polynomial is like this. Add the exponents and change it's positions depending on it's degree.
3a³b - 45b³ + ab + 5b + 6 + 4a²b³
4a²b³ + 3a³b - 45b³ + ab + 5b + 6
I hope it help. ☺