It is simple. In the menu, go to Administration, Synaptic and when it asks
provide your password. Then Click on Search (not Quick Search which should
be changed to avoid confusion to Filter which is all it really does) and
type: task juggler

Then if you want to install it, right click and choose Mark for
Installation. Choose as many packages as you want. When done, hit the Apply
button. It will ask for confirmation in a popup then click Apply again. Then
wait for it to end. The advantage of Synaptic over Software Centre is that
you can select multiple packages before you download instead of doing each
one separately which for me is a pain. I hate waiting when I could be doing
something else.