Truth-tables won't help you; you need to get the right translation in the first place.
One important distinction that often helps with these translations is to distinguish between sufficient conditions and necessary conditions.
Here is an example to illustrate the difference: to be a bachelor, you need to be unmarried. So: Bachelor => Unmarried. Being unmarried is thus a necessary condition for being a bachelor. But is it sufficient? Is anyone who is unmarried a bachelor? Clearly not: unmarried females are not bachelors. So, we don't have Unmarried => Bachelor. We can say, however, that being a bachelor is a sufficient condition for being unmarried. That is: once we know someone is a bachelor, then we know the person is unmarried. So, once again we have Bachelor => Unmarried.
Contrapositives can also often help you with making sense of these conditionals. For example, note that anyone who is married is not a bachelor. So, we have NOT Unmarried => NOT Bachelor. But the contrapositive of that is: Bachelor => Unmarried.
A final and simple trick is specific to the 'unless': read the 'unless' as 'if not'!
Now, let's apply these strategies to your statements:
The first statement, which states that Joel is happy whenever Anna is happy, is a good example of a sufficient condition. Apparently Anna being happy is sufficient for Joel to be happy. Or, in logic in terms: if we know that Anna is happy, then we immediately know that Joel is happy: nothing else needs to happen for Joel to be happy. So, this translates to AnnaHappy => JoelHappy
The second statement, which says that Joel is happy only if Anna is happy, is a good example of a necessary condition: Anna being happy is a necessary condition for Joel to be happy. Thus, Anna being happy may not be by itself sufficient for Joel to be happy. So, this time we can't say AnnaHappy => JoelHappy. We can, however, say JoelHappy => AnnaHappy: when we see Joel being happy, we can infer that Anna must be happy as well, because the only way for Joel to be happy is for Anna to be happy.
We can also use the contrapositive here: if Anna is not happy, then Joel will definitely not be happy either, and so we have NOT AnnaHappy => NOT JoelHappy, which by contraposition is the same as JoelHappy => AnnaHappy
Finally, for the third sentence 'Joel is happy unless Anna is not happy', we use the trick as indicated, and re[phrase this as 'Joel is happy if not Anna is not happy' ... which works out to: NOT NOT AnnaHappy > JoelHappy, and thus to AnnaHappy > JoelHappy