When you have decided that a thing ought to be done and are doing it, never avoid being seen doing it, though the many shall form an unfavorable opinion about it. For if it is not right to do it, avoid doing the thing; but if it is right, why are you afraid of those who shall find fault wrongly?
I mentioned this quote on a forum a little while back, and was suprised by the response, though in hindsight it makes sense. Some people took it to mean the same thing as the dictatorial favourite:
if you have nothing to hide, you have nothing to fear
In the context of Stoicism however, you should have nothing to fear anyway. Remember, people only hold the power over us that we give them. From a practical point of view, perhaps it would be allowable to hide your righteous actions from a evil party, if that allows you to continue your good work.
That of course is an extreme situation: in most of our lives, it is not fear of physical punishment that makes us want to hide our actions, but fear of what other people think of us. In which case, Epictetus' advice is quite straight forward: if you are being righteous, regardless of how others judge you, you should be open about your actions. Righteousness of course in the Stoic sense is the persuit of philosophy; of personal growth; and of self control.
Note that Epictetus does not tell you to preach or brag about your actions, merely to not hide them.