Quote Originally Posted by Евгения Белякова
How is this said correctly:

Я ещё не составляла..(или составила?)

You don't need to translate the verb, please don't, because actually I can't remember the English meaning(i only know what it means in Russian). But what is the difference between these forms?
It's the difference between perfective and imperfective aspects. An imperfective (составляла - составлять) has a meaning of the long or incomplete action, as you were doing it for some time and haven't finished yet. It's similar to a continuous tense in English. On the other hand, a perfective aspect (составила - составить) has a meaning of the complete action, mostly in the past. That's the thing you already have done, similar to a perfect tenses in English.

So, "я не составляла" - "I didn't do it, didn't even start to do it"; "я не составила" - "I haven't finished yet", may be you have already started, but haven't finished.