In WordList, open an index as you would any other kind of word-list file -- using File | Open. The filename will end .tokens. Easier, in the Controller | Previous lists, choose any index you've made and double-click it.
The index looks exactly like a large word-list. (Underneath, it "knows" a lot more and can do more but it looks the same.)
The picture above shows the top 10 words in the BNC Corpus. Number 5 (#) represents numbers or words which contain numbers such as £50.00. These very frequent words are also very consistent -- they appear in at least 99% of the 4,054 texts of BNC.
In the view below, you see words sorted by the number of Texts: all these words appeared 10 times in the corpus but their frequencies vary.
You can highlight one or more words or mark them with the option, then to get a speedy concordance.
But its best use to start with is to generate word clusters like these: