The core idea of the Omega System is very simple: Anything a character attempts is assigned a Task Rating, and the player rolls 1d20, aiming for as low a roll as possible.
A roll above the TR is a failure, a roll under the TR succeeds.
Should more detail be required, the Quality Level Table is consulted. Cross-reference the TR with the difference between the roll and the TR (subtract roll from TR). This shows the Quality Level of the success.
If you want a hard copy of this table, download an Excel version here, or just right-click the table and Save As...(it's a PNG)