Make sure email notifications are enabled for new assignments.
Collect more points so you can also start doing more difficult translations
If you've done a good job on your translation, you will receive points. If you collect enough points (the amount is displayed in your account), you will go up a level. After you reach a higher level, you also can work on more difficult texts and earn more per word.
Responding quickly to open assignments
All assignments are emailed to suitable translators every 2 hours based on language pair and the difficulty of the text. But you can take on the assignments before those times. Just sign into your account and look for open assignments. Assignments are given on a first come, first served basis. So you can get more work by acting fast.
You might be interested in these FAQ questions
How many (test) assignments should I expect