If you find yourself looking at the task page and there is nothing to do - don't worry, there's normally a logical reason!
It may be that the Project Owner needs to add some tasks first, this can happen if its a new project
It may be you have completed all the available tasks - if so, wait for the Project Owner to add some new ones
Be aware that tasks can be setup so that you can complete them only once. Once done, they disappear from the list. When this happens it up to the Project Owner to add more.