I think some of the people above got confused over citing and having the resource at all.
You asked about citing resources - they answered defensively without reason.
You were clearly asking about how YOU use eSword material. Correct me if I'm wrong.
Actually each source will usually have it's own rules of citing (i.e. for non-private usage).
It very often goes something like this
"you may quote up to 500 words from the text as long as you quote the copyright notice"
If you just say "NKJV John chapters 1-7" you are citing a lot more but you are NOT showing the content. The user would have to HAVE the NKJV to see the verses directly mentioned. This is ALWAYS acceptable (unless you are stating things about state secrets, spy stuff, or secret patented business stuff).
The same applies to books. I could say "Dawkins The God Delusion p16, para. 2" without problem. If I express it in text (i.e. print it out) I would have to adhere to the copyright rules stated in that book. I WOULD probably be allowed to do it if I quoted the copyright notice (i.e. where the quotation was from and who it belonged to) as long as it did not cross the threshold of what they allow (usually a number of words).
A properly crafted e-Sword file should include the copyright information in it's metadata (data you don't normally see).
Clicking the tab "Bible->Information" does not always give more than the basic copyright info - often it does though and one should look there first. The same applies for other sources (commentaries, etc.).
To be totally safe check out the BibleSupport page for the resource - as it might contain info otherwise unexpressed (which we have to agree we have read when we download something so...)
If in doubt don't go more than a couple of hundred words - and say what the source (who and what) you got it from is. It need only be a small addition in brackets on a slide, or a brief comment in a presentation (unless the credit is on screen or print that accompanies the presentation - if you record the presentation you should supply with it the accreditation of the works you quote - though it's only usual in academic circles to do so).